POC: allow to buffer messages in save

[DavidBadura]

Storing 10k aggregates takes 8 seconds, which is very long.
As a proof of concept, I added a flag, which buffers messages and may solve the problem if you use transactions.

[github-actions]

Hello 👋

here is the most recent benchmark result:

SplitStreamBench
================

+-------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                         | time (kde mode)                                     | memory                                     |
+-------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                 | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+-------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchLoad10000Events () | 4.800ms (±0.00%)   | 4.930ms (±0.00%)   | -2.64%    | 38.098mb        | 37.578mb   | +1.39%      |
| benchSave10000Events () | 342.322ms (±0.00%) | 357.293ms (±0.00%) | -4.19%    | 37.599mb        | 37.070mb   | +1.43%      |
+-------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

SimpleSetupBench
================

+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                                        | time (kde mode)                                     | memory                                     |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                                | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchLoad1Event ()                     | 23.014ms (±0.00%)  | 979.400μs (±0.00%) | +2249.77% | 33.498mb        | 33.761mb   | -0.78%      |
| benchLoad10000Events ()                | 71.192ms (±0.00%)  | 50.238ms (±0.00%)  | +41.71%   | 33.498mb        | 33.761mb   | -0.78%      |
| benchSave1Event ()                     | 86.500μs (±0.00%)  | 842.700μs (±0.00%) | -89.74%   | 14.295mb        | 33.761mb   | -57.66%     |
| benchSave10000Events ()                | 11.804ms (±0.00%)  | 218.787ms (±0.00%) | -94.60%   | 115.504mb       | 33.761mb   | +242.12%    |
| benchSave10000Aggregates ()            | 838.573ms (±0.00%) | 6.508s (±0.00%)    | -87.12%   | 26.731mb        | 33.761mb   | -20.82%     |
| benchSave10000AggregatesTransaction () | 605.562ms (±0.00%) | 4.713s (±0.00%)    | -87.15%   | 47.136mb        | 33.762mb   | +39.62%     |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

SnapshotsBench
==============

+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                                        | time (kde mode)                                     | memory                                     |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                                | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchLoad10000EventsMissingSnapshot () | 50.199ms (±0.00%)  | 50.379ms (±0.00%)  | -0.36%    | 34.291mb        | 33.762mb   | +1.57%      |
| benchLoad10000Events ()                | 847.100μs (±0.00%) | 874.200μs (±0.00%) | -3.10%    | 34.291mb        | 33.762mb   | +1.57%      |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

PersonalDataBench
=================

+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                                        | time (kde mode)                                     | memory                                     |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                                | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchLoad1Event ()                     | 886.800μs (±0.00%) | 934.300μs (±0.00%) | -5.08%    | 35.420mb        | 34.891mb   | +1.51%      |
| benchLoad10000Events ()                | 82.746ms (±0.00%)  | 84.504ms (±0.00%)  | -2.08%    | 35.420mb        | 34.891mb   | +1.51%      |
| benchSave1Event ()                     | 1.345ms (±0.00%)   | 1.389ms (±0.00%)   | -3.20%    | 35.420mb        | 34.891mb   | +1.51%      |
| benchSave10000Events ()                | 247.125ms (±0.00%) | 246.192ms (±0.00%) | +0.38%    | 35.422mb        | 34.893mb   | +1.51%      |
| benchSave10000Aggregates ()            | 10.250s (±0.00%)   | 10.351s (±0.00%)   | -0.98%    | 35.420mb        | 34.891mb   | +1.51%      |
| benchSave10000AggregatesTransaction () | 8.755s (±0.00%)    | 8.756s (±0.00%)    | -0.02%    | 35.420mb        | 35.392mb   | +0.08%      |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

SubscriptionEngineBench
=======================

+---------------------------+-----------------+-----------------+-----------+-----------------+------------+-------------+
|                           | time (kde mode)                               | memory                                     |
+---------------------------+-----------------+-----------------+-----------+-----------------+------------+-------------+
| subject                   | Tag: <current>  | Tag: base       | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+---------------------------+-----------------+-----------------+-----------+-----------------+------------+-------------+
| benchHandle10000Events () | 3.078s (±0.00%) | 3.095s (±0.00%) | -0.57%    | 34.689mb        | 34.161mb   | +1.55%      |
+---------------------------+-----------------+-----------------+-----------+-----------------+------------+-------------+

This comment gets update everytime a new commit comes in!