fix: ObservableCounter and ObservableUpDownCounter remove stale attribute combinations that are no longer observed

[taisho6339]

Fixes #3213

Changes

ObservableCounter and ObservableUpDownCounter now correctly report only data points from the current measurement cycle, removing stale attribute combinations that are no longer observed.

Merge requirement checklist

• [x] CONTRIBUTING guidelines followed
• [x] Unit tests added/updated (if applicable)
• [x] Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• [ ] Changes in public API reviewed (if applicable)

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: taisho6339 / name: Hiroki Sakamoto (e98c4fd5bf4b7060d3acdce13f455d714ef0d3fe)

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 80.7%. Comparing base (65969fd) to head (e98c4fd).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3248     +/-   ##
=======================================
- Coverage   80.7%   80.7%   -0.1%     
=======================================
  Files        129     129             
  Lines      23210   23203      -7     
=======================================
- Hits       18748   18741      -7     
  Misses      4462    4462             

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[cijothomas]

Sorry for the delay. I'll review soon.