fix: serialization/deserialization for u64, f64, and "NaN" float fields in Metrics

[parmesant]

Fixes #2487
Design discussion issue (if applicable) #

Changes

This PR adds to the changes made by @lalitb in his PR #2491

For metric type Summary, quantileValues.quantile gets treated as u64 and not f64 when its value is 1

Also, flags comes optionally in the payload hence added default to it (and some other fields)

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)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: lalitb / name: Lalit Kumar Bhasin (18b7c71, 8d57a93, da5ed50, e7e3b39, eefc117)
• ✅ login: parmesant / name: Anant Vindal (196d926, 45fb828)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.5%. Comparing base (07bb613) to head (45fb828).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3284   +/-   ##
=====================================
  Coverage   80.5%   80.5%           
=====================================
  Files        129     129           
  Lines      23286   23286           
=====================================
  Hits       18748   18748           
  Misses      4538    4538           

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