Some additional accessibility test coverage

[jonathanmos]

What does this PR do?

Adds some additional test coverage for accessibility around the logic for view reduction, and also minor code cleanup.

Motivation

What inspired you to submit this pull request?

Additional Notes

Anything else we should know when reviewing?

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.92%. Comparing base (c6b7a43) to head (aedbf98).
⚠️ Report is 6 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2823      +/-   ##
===========================================
- Coverage    70.18%   69.92%   -0.26%     
===========================================
  Files          834      834              
  Lines        31296    31296              
  Branches      5259     5259              
===========================================
- Hits         21964    21883      -81     
- Misses        7883     7925      +42     
- Partials      1449     1488      +39     

Files with missing lines	Coverage Δ
...kotlin/com/datadog/android/rum/RumConfiguration.kt	97.44% <ø> (ø)

... and 36 files with indirect coverage changes

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[0xnm]

I think there is a disconnect between RumViewScope (or AccessibilitySnapshotManager) and RumDataWriter leading to the existence of RumDataWriter.isAccessibilityPopulated method and following issues:

• one may update DefaultAccessibilitySnapshotManager.latestSnapshot method if new properties are added, but forget to update RumDataWriter.isAccessibilityPopulated
• the number of properties participating in DefaultAccessibilitySnapshotManager.latestSnapshot is not the same as in RumDataWriter.isAccessibilityPopulated, is it expected?
• as a consequence of above, we have some properties which are not checked for the change in DefaultAccessibilitySnapshotManager.latestSnapshot, meaning we will always have hasAccessibility=true, isn't it?

Maybe we should simply return null from DefaultAccessibilitySnapshotManager.latestSnapshot if nothing changed? And rename this method somehow.

This would allow us to have better encapsulation and smaller change surface.