Fix aggregation bug due to stale hash value

[cijothomas]

Fixes #1418 Accidental side effect of this PR: https://github.com/open-telemetry/opentelemetry-rust/pull/1407

Changes

Re-calculates hash, if attributes are changed, which can occur when View is configured to drop attributes. Not adding changelog, as this can be part of the #1407 itself, and we haven't released with that yet.

Merge requirement checklist

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

[cijothomas]

Maybe better to fold this into https://github.com/open-telemetry/opentelemetry-rust/pull/1421

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 67.8%. Comparing base (35c7803) to head (eda0001). Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1422     +/-   ##
=======================================
+ Coverage   67.3%   67.8%   +0.4%     
=======================================
  Files        138     139      +1     
  Lines      19654   19687     +33     
=======================================
+ Hits       13243   13363    +120     
+ Misses      6411    6324     -87     

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[cijothomas]

Maybe better to fold this into #1421

This needs to proceed as-is now, as 1421 is reverted.