timeseries [3/6] RUM-13949: Add CPU timeseries data-point reader and serializer

[satween]

What does this PR do?

Adds CpuDatapointReader, which reads CPU-usage metrics from the existing CpuVitalReader vital and wraps them as DataPoint values; and CpuEventSerializer, which converts a batch of CPU DataPoints into a RumTimeseriesCpuEvent JSON object ready for ingestion.

Motivation

Implements CPU metric collection as the first concrete timeseries type, exercising the pipeline infrastructure introduced in the previous commit.

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)

[satween]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• timeseries [6/6] RUM-13949 Add end-to-end timeseries verification tests with CSV fixtures #3436
• timeseries [5/6] RUM-13949 Wire timeseries collection into RUM session lifecycle #3435
• timeseries [4/6] RUM-13949 Add memory timeseries serializer and session factory #3434
• timeseries [3/6] RUM-13949: Add CPU timeseries data-point reader and serializer #3433 👈 (View in Graphite)
• timeseries [2/6] RUM-13949: Implement timeseries pipeline infrastructure #3432
• timeseries RUM-13949: Add timeseries JSON schemas and regenerate API surface #3431
• feature/timeseries

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 95.05495% with 9 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (tvaleev/feature/RUM-13949/timeseries-pipeline-infrastructure@1a11660). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...internal/timeseries/provider/CpuDatapointReader.kt	79.17%	0 Missing and 5 partials ⚠️
...ternal/timeseries/serializer/CpuEventSerializer.kt	95.92%	0 Missing and 2 partials ⚠️
...atadog/android/rum/internal/timeseries/Pipeline.kt	91.67%	0 Missing and 1 partial ⚠️
...m/internal/timeseries/RumSessionScopeTimeseries.kt	96.77%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                                       Coverage Diff                                       @@
##             tvaleev/feature/RUM-13949/timeseries-pipeline-infrastructure    #3433   +/-   ##
===============================================================================================
  Coverage                                                                ?   72.37%           
===============================================================================================
  Files                                                                   ?      974           
  Lines                                                                   ?    35743           
  Branches                                                                ?     5959           
===============================================================================================
  Hits                                                                    ?    25868           
  Misses                                                                  ?     8253           
  Partials                                                                ?     1622           

Files with missing lines	Coverage Δ
.../datadog/android/rum/internal/RumSessionTypeExt.kt	100.00% <100.00%> (ø)
...droid/rum/internal/domain/scope/RumSessionScope.kt	91.81% <100.00%> (ø)
.../datadog/android/rum/internal/timeseries/Buffer.kt	100.00% <100.00%> (ø)
...tadog/android/rum/internal/timeseries/DataPoint.kt	100.00% <100.00%> (ø)
...nal/timeseries/RumSessionScopeTimeseriesFactory.kt	100.00% <100.00%> (ø)
...m/internal/timeseries/provider/DataPointsReader.kt	100.00% <100.00%> (ø)
...atadog/android/rum/internal/timeseries/Pipeline.kt	93.75% <91.67%> (ø)
...m/internal/timeseries/RumSessionScopeTimeseries.kt	95.74% <96.77%> (ø)
...ternal/timeseries/serializer/CpuEventSerializer.kt	95.92% <95.92%> (ø)
...internal/timeseries/provider/CpuDatapointReader.kt	79.17% <79.17%> (ø)

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