chore(internal): fix CI Visibility usage of the core API

[brettlangdon]

Fixes some small inconsistencies with the core api usage in CI Visibility.

1. A call to dispatch_with_results when no value is expected to be returned (small performance optimization to avoid building a results dictionary when it isn't needed).
2. A call to dispatch_with_results which would not return the underlying listener value
   a. (I think it would always return a falsey value since it should have been returning the core._MissingEvent EventResult which is falsey and which has a value of None... ?)

I am not sure which tests should be evaluated/updated, since I am surprised there weren't any failing tests before, there should have been.

Checklist

• Change(s) are motivated and described in the PR description
• Testing strategy is described if automated tests are not included in the PR
• Risks are described (performance impact, potential for breakage, maintainability)
• Change is maintainable (easy to change, telemetry, documentation)
• Library release note guidelines are followed or label changelog/no-changelog is set
• Documentation is included (in-code, generated user docs, public corp docs)
• Backport labels are set (if applicable)
• If this PR changes the public interface, I've notified @DataDog/apm-tees.

Reviewer Checklist

• Title is accurate
• All changes are related to the pull request's stated goal
• Description motivates each change
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Change is maintainable (easy to change, telemetry, documentation)
• Release note makes sense to a user of the library
• Author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[emmettbutler]

Oh yeah, it's not clear at all to me why this isn't causing test_is_item_itr_skippable_test_level to fail in current main. This change does look more correct, though.

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-05-15 08:23:13

Comparing candidate commit 197c676 in PR branch brettlangdon/fix.ci.core.api.usage with baseline commit 5148d18 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 209 metrics, 9 unstable metrics.

[romainkomorndatadog]

These (the settings request) aren't in use yet so they're not tested (and, clearly, not working either).

edit: the external API is_item_itr_skippable() static method (that ends up calling core.dispatch_with_results("ci_visibility.itr.is_item_skippable") itself) is also not tested yet.

test_is_item_itr_skippable_test_level is directly testing the CIVisibility.is_item_itr_skippable() function directly (which is why it's in test_ci_visibility.py), so any changes in this PR wouldn't affect its results.

I'll take over the PR.

[romainkomorndatadog]

Renaming this to a chore because this API isn't released yet, so it's not a "fix".