[sdk-metrics] Stablize MetricPoint reclaim feature for delta aggregation

[xiang17]

Fixes #5443
Design discussion issue #5443

Changes

Please provide a brief description of the changes here.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable): N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.56%. Comparing base (6250307) to head (394275f).
Report is 377 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5956      +/-   ##
==========================================
+ Coverage   83.38%   86.56%   +3.17%     
==========================================
  Files         297      262      -35     
  Lines       12531    11782     -749     
==========================================
- Hits        10449    10199     -250     
+ Misses       2082     1583     -499     

Flag	Coverage Δ
unittests	?
unittests-Project-Experimental	86.29% <100.00%> (?)
unittests-Project-Stable	86.50% <100.00%> (?)

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

Files with missing lines	Coverage Δ
src/OpenTelemetry/Metrics/AggregatorStore.cs	86.17% <100.00%> (+5.78%)	⬆️
src/OpenTelemetry/Metrics/MeterProviderSdk.cs	93.30% <100.00%> (+5.46%)	⬆️
src/OpenTelemetry/Metrics/Metric.cs	97.24% <ø> (+0.71%)	⬆️
...c/OpenTelemetry/Metrics/MetricPoint/MetricPoint.cs	94.24% <100.00%> (ø)
...rc/OpenTelemetry/Metrics/Reader/MetricReaderExt.cs	91.81% <ø> (ø)

... and 237 files with indirect coverage changes

[CodeBlanch]

LGTM

[Kielek]

@xiang17, can this class be fully removed and replaced by MetricSnapshotTests without any inheritance?

[CodeBlanch]

#5960