Update metrics benchmarks

[utpilla]

Changes

• Update Histogram benchmark to use iter_batched to exclude the setup time from the measurement. Similar to what Exclude benchmark setup duration using iter_batched #2233 did for Counter
• Add a benchmark to test attribute values that non-static string slices to both Counter and Histogram (Address Update KeyValue to avoid copying non-static string slices #2089 (comment))

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)

[utpilla]

With #2089, we would be able to simply pass a string slice and avoid the string allocation:

Suggested change

	attribute_values[index_first_attribute].as_str().to_owned(),
	attribute_values[index_first_attribute].as_str(),

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.9%. Comparing base (a1dda22) to head (5f0e3d4).
Report is 2 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2502   +/-   ##
=====================================
  Coverage   77.9%   77.9%           
=====================================
  Files        123     123           
  Lines      22888   22888           
=====================================
  Hits       17839   17839           
  Misses      5049    5049           

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