fix metrics race condition

[esigo]

Fixes #1542 (issue)

Changes

protects reads in aggregations.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #1552 (88a314b) into main (4cf41c4) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1552      +/-   ##
==========================================
- Coverage   83.35%   83.32%   -0.02%     
==========================================
  Files         156      156              
  Lines        4970     4975       +5     
==========================================
+ Hits         4142     4145       +3     
- Misses        828      830       +2     

Impacted Files	Coverage Δ
...ry/sdk/metrics/aggregation/histogram_aggregation.h	90.00% <ø> (ø)
...ry/sdk/metrics/aggregation/lastvalue_aggregation.h	0.00% <ø> (ø)
...elemetry/sdk/metrics/aggregation/sum_aggregation.h	0.00% <ø> (ø)
...k/src/metrics/aggregation/histogram_aggregation.cc	87.76% <100.00%> (+0.26%)	⬆️
...k/src/metrics/aggregation/lastvalue_aggregation.cc	37.50% <100.00%> (+2.02%)	⬆️
sdk/src/metrics/aggregation/sum_aggregation.cc	80.36% <100.00%> (+0.36%)	⬆️
ext/src/http/client/curl/http_client_curl.cc	80.31% <0.00%> (-1.13%)	⬇️
sdk/src/trace/batch_span_processor.cc	91.41% <0.00%> (+0.79%)	⬆️