MetricStorage dtors

[esigo]

Adds missing MetricStorage virtual dtors

Please provide a brief description of the changes here.

Also adds clangd cache to gitignore.

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

[lalitb]

Thanks for the fix.

[codecov]

Codecov Report

Merging #1270 (a3bf48d) into main (0b1a74c) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1270      +/-   ##
==========================================
+ Coverage   92.37%   92.37%   +0.01%     
==========================================
  Files         202      203       +1     
  Lines        7336     7338       +2     
==========================================
+ Hits         6776     6778       +2     
  Misses        560      560              

Impacted Files	Coverage Δ
...e/opentelemetry/sdk/metrics/state/metric_storage.h	100.00% <100.00%> (ø)