Reset scale of exponential histogram

[hannahhaering]

Fixes #5635

Changes

Reset scale to 20 of the Base2 Exponential Bucket Histogram after each collection cycle when using delta aggregation temporality.

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)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.69%. Comparing base (8b3d8fa) to head (fb421b9).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6557      +/-   ##
==========================================
+ Coverage   86.38%   86.69%   +0.30%     
==========================================
  Files         258      258              
  Lines       11909    11910       +1     
==========================================
+ Hits        10288    10325      +37     
+ Misses       1621     1585      -36     

Flag	Coverage Δ
unittests-Project-Experimental	86.61% <100.00%> (+0.26%)	⬆️
unittests-Project-Stable	86.53% <100.00%> (+0.16%)	⬆️

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

Files with missing lines	Coverage Δ
...ics/MetricPoint/Base2ExponentialBucketHistogram.cs	100.00% <100.00%> (ø)
...c/OpenTelemetry/Metrics/MetricPoint/MetricPoint.cs	94.17% <100.00%> (-0.07%)	⬇️

... and 4 files with indirect coverage changes

[martincostello]

Seems reasonable to me. Please update the CHANGELOG.

[github-actions]

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