[pdata] Fix Map.EnsureCapacity bug when the Map is not empty

[tigrannajaryan]

EnsureCapacity was incorrectly clearing the Map when increasing the capacity. It will now correctly preserve existing elements.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.02 🎉

Comparison is base (9375d95) 90.82% compared to head (aba3d9d) 90.85%.

❗ Current head aba3d9d differs from pull request most recent head f36886f. Consider uploading reports for the commit f36886f to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8040      +/-   ##
==========================================
+ Coverage   90.82%   90.85%   +0.02%     
==========================================
  Files         300      300              
  Lines       15108    15108              
==========================================
+ Hits        13722    13726       +4     
+ Misses       1112     1109       -3     
+ Partials      274      273       -1     

Impacted Files	Coverage Δ
pdata/pcommon/map.go	93.95% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[codeboten]

Minor typo, otherwise looks good.