Fix metrics aggregation bug for Sum and Precomputed Sum to avoid duplicate export

[utpilla]

We missed adding a few HashSet checks to avoid duplicate exports in #1989. The affected aggregations are:

• Sum (Cumulative)
• PrecomputedSum (Delta)
• PrecomputedSum (Cumulative)

Changes

• Fix the affected aggregations
• Update the existing related tests to test for both Delta and Cumulative temporality

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)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.1%. Comparing base (07b918d) to head (a3cfaaf).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2018   +/-   ##
=====================================
  Coverage   76.1%   76.1%           
=====================================
  Files        122     122           
  Lines      20684   20700   +16     
=====================================
+ Hits       15750   15766   +16     
  Misses      4934    4934           

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[cijothomas]

more gaps in testing identified.
As mentioned in community call, I'll do a full check on the overall coverage, and reorganize the tests so it is easy to tell what is covered and what is not!

Thanks!