Avoid Boxing/Unboxing on accessing elements of VBufferDataFrameColumn (fix merge issues)

[asmirnov82]

Fixes #6864

[codecov]

Codecov Report

Merging #6867 (67036d0) into main (766569b) will decrease coverage by 0.02%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##             main    #6867      +/-   ##
==========================================
- Coverage   69.40%   69.39%   -0.02%     
==========================================
  Files        1238     1238              
  Lines      249441   249441              
  Branches    25522    25520       -2     
==========================================
- Hits       173130   173105      -25     
- Misses      69692    69716      +24     
- Partials     6619     6620       +1     

Flag	Coverage Δ
Debug	69.39% <60.00%> (-0.02%)	⬇️
production	63.92% <60.00%> (-0.02%)	⬇️
test	88.90% <ø> (ø)

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Files	Coverage Δ
.../Microsoft.Data.Analysis/VBufferDataFrameColumn.cs	45.77% <60.00%> (-1.41%)	⬇️

... and 7 files with indirect coverage changes