Clean up PrimitiveColumnContainer

[JakeRadMSFT]

I was inspired by a community members PR (#6642) to try and clean up PrimitiveColumnContainer.

I'd say this is Part 1 of a few part series for improving DataFrame.

• Updates the code to be more consistent with the Buffer and nullBufferBitMap usage
• Updated all the PrimitiveColumn related things that used to be T : struct and move to T : unmanaged.
• Hopefully improved readability

Not Fixed:

• It's still not thread safe

[agocke]

Out of curiosity, what is the contract for this method? It's going to swap out the buffer in the array with a new one -- what if someone's holding on to the old one? How do you handle reference invalidation?

[JakeRadMSFT]

I just inherited this but my understanding is the following:

• This method is going to apply func for each element and update the value in buffer
  • It will make the buffer mutable if it needs to
  • It will update the nullBitMapBuffer

If something is holding on to the old buffer - it shouldn't be/it's outdated.

[codecov]

Codecov Report

Merging #6656 (e33608d) into main (3986fcf) will decrease coverage by 0.01%.
The diff coverage is 90.74%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6656      +/-   ##
==========================================
- Coverage   68.59%   68.59%   -0.01%     
==========================================
  Files        1200     1201       +1     
  Lines      250326   250296      -30     
  Branches    26096    26094       -2     
==========================================
- Hits       171701   171679      -22     
+ Misses      71809    71803       -6     
+ Partials     6816     6814       -2     

Flag	Coverage Δ
Debug	68.59% <90.74%> (-0.01%)	⬇️
production	63.07% <90.74%> (-0.01%)	⬇️
test	88.84% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/Microsoft.Data.Analysis/DataFrameBuffer.cs	82.60% <ø> (ø)
...lysis/PrimitiveColumnContainer.BinaryOperations.cs	84.21% <ø> (ø)
...ata.Analysis/PrimitiveDataFrameColumnArithmetic.cs	48.98% <ø> (ø)
...a.Analysis/PrimitiveDataFrameColumnComputations.cs	45.66% <ø> (ø)
...Microsoft.Data.Analysis/ReadOnlyDataFrameBuffer.cs	47.36% <ø> (ø)
...icrosoft.Data.Analysis/PrimitiveColumnContainer.cs	83.04% <88.63%> (+0.03%)	⬆️
...t.Data.Analysis/PrimitiveColumnContainerHelpers.cs	100.00% <100.00%> (ø)

... and 6 files with indirect coverage changes