MetricRefactor - Part1 - Move AttributeSet inside aggregations

[cijothomas]

Part 1 of metric sdk refactor to achieve perf gains and no-heap-allocation. The heap allocation and perf cost is due to the usage of AttributeSet which clones and stores the incoming slice of KV pairs, after sorting + de-duplicating, which can be eliminated.

This PR modifies traits to only need &[KeyValue] (which is what API accepts from user) instead of AttributeSet. There is no perf gain in this PR, as the AttributeSet is still constructed inside each aggregations. This is done to keep the scope of PR very small, and easy to review.
In the next PR, Sum aggregation will be targeted to achieve the perf gains and no-heap alloc, later extending to other instruments.

[codecov]

Codecov Report

Attention: Patch coverage is 87.23404% with 6 lines in your changes missing coverage. Please review.

Project coverage is 74.8%. Comparing base (cfbd1c3) to head (7a38c79).

Files	Patch %	Lines
opentelemetry-sdk/src/metrics/mod.rs	0.0%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1977     +/-   ##
=======================================
- Coverage   74.9%   74.8%   -0.1%     
=======================================
  Files        122     122             
  Lines      20411   20429     +18     
=======================================
+ Hits       15296   15298      +2     
- Misses      5115    5131     +16     

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[utpilla]

Looks good! Left some suggestions.

[lalitb]

LGTM. These seems to be all internal changes, so no changelog required.