Advertise SCRAM / SASL support in addition to PLAIN

[henvic]

Description

• Add SCRAM SHA-1 and SHA-256 to getParameter command.
• Add SASL Supported Mechanisms to hello command.

Closes #3778.

Readiness checklist

• I added/updated unit tests (and they pass).
• I added/updated integration/compatibility tests (and they pass).
• I added/updated comments and checked rendering.
• I made spot refactorings.
• I updated user documentation.
• I ran task all, and it passed.
• I ensured that PR title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Milestone (Next), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

Attention: Patch coverage is 76.11940% with 16 lines in your changes are missing coverage. Please review.

Project coverage is 73.78%. Comparing base (5a5ca29) to head (ceadf72).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4113      +/-   ##
==========================================
- Coverage   74.31%   73.78%   -0.53%     
==========================================
  Files         353      353              
  Lines       22738    22789      +51     
==========================================
- Hits        16897    16816      -81     
- Misses       4552     4693     +141     
+ Partials     1289     1280       -9     

Files	Coverage Δ
integration/setup/helpers.go	93.93% <ø> (+15.15%)	⬆️
internal/handler/msg_getparameter.go	93.42% <100.00%> (ø)
internal/handler/msg_usersinfo.go	76.72% <100.00%> (ø)
internal/handler/msg_hello.go	75.34% <75.38%> (-15.57%)	⬇️

... and 12 files with indirect coverage changes

Flag	Coverage Δ
filter-true	67.22% <76.11%> (-0.60%)	⬇️
hana-1	?
integration	67.22% <76.11%> (-0.60%)	⬇️
mongodb-1	4.87% <0.00%> (+0.13%)	⬆️
postgresql-1	48.43% <26.86%> (+0.24%)	⬆️
postgresql-2	47.20% <26.86%> (-1.39%)	⬇️
postgresql-3	49.41% <74.62%> (+0.32%)	⬆️
sqlite-1	47.57% <26.86%> (+0.23%)	⬆️
sqlite-2	46.36% <26.86%> (-1.43%)	⬇️
sqlite-3	48.64% <74.62%> (+0.46%)	⬆️
unit	32.49% <0.00%> (-0.08%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

[chilagrow]

Just a small comment 🤗

[rumyantseva]

Looks good to me!

[AlekSi]

There are three quirks that I pointed out many times over multiple PRs:

1. The usage of else when the code without it would be easier to understand (by having fewer branches). That's a generalization of https://go.dev/wiki/CodeReviewComments#indent-error-flow that is already mentioned in CONTRIBUTING.md, but we probably could add to the list of our idiosyncrasies.
2. The usage of assert instead of require even if the test can't continue. That small detail becomes pretty important when we add another backend – the test process crashes instead of just marking a test as a failure.
3. The creation of new test helpers. I don't think the more, the merrier rule applies there – the list of existing helpers one has to check to decide if they should be used or not should be smaller, not larger, especially if some of them are used only once.

So please be aware of those things and try not to repeat them again.
@FerretDB/core, please don't ignore those things in your reviews.

[chilagrow]

Very minor comments

[rumyantseva]

LGTM