RUM-16325 timeseries: Post-review fixes for timeseries

[satween]

What does this PR do?

Applies post-review fixes from PR on top of the schema update: adjustments to RumFeature, RumSessionScope, TimeseriesConfiguration, and the CPU/Memory event serializers, plus added/updated unit and end-to-end tests.

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

❌ Patch coverage is 81.25000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.56%. Comparing base (147653a) to head (b4386f7).

Files with missing lines	Patch %	Lines
...lin/com/datadog/android/rum/internal/RumFeature.kt	50.00%	2 Missing ⚠️
.../android/rum/timeseries/TimeseriesConfiguration.kt	66.67%	1 Missing ⚠️

Additional details and impacted files

@@                                  Coverage Diff                                   @@
##           tvaleev/feature/timeseries-RUM-16325-schema-update    #3556      +/-   ##
======================================================================================
- Coverage                                               72.59%   72.56%   -0.03%     
======================================================================================
  Files                                                     980      980              
  Lines                                                   36053    36056       +3     
  Branches                                                 6033     6031       -2     
======================================================================================
- Hits                                                    26171    26163       -8     
- Misses                                                   8197     8205       +8     
- Partials                                                 1685     1688       +3     

Files with missing lines	Coverage Δ
...kotlin/com/datadog/android/rum/RumConfiguration.kt	92.47% <ø> (ø)
...droid/rum/internal/domain/scope/RumSessionScope.kt	92.00% <100.00%> (+0.19%)	⬆️
...ternal/timeseries/serializer/CpuEventSerializer.kt	90.38% <100.00%> (+3.85%)	⬆️
...nal/timeseries/serializer/MemoryEventSerializer.kt	91.23% <100.00%> (+3.51%)	⬆️
.../android/rum/timeseries/TimeseriesConfiguration.kt	90.91% <66.67%> (ø)
...lin/com/datadog/android/rum/internal/RumFeature.kt	91.82% <50.00%> (+0.19%)	⬆️

... and 29 files with indirect coverage changes

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