Merge SqlColumnEncryptionCertificateStoreProvider

[edwardneal]

Contributes to #1261.

This sits alongside #2501, and ports the SqlColumnEncryptionCertificateStoreProvider class. Once again, this version uses the .NET approach of SHA256.Create() rather than the .NET Framework approach of constructing a new SHA256Cng instance.

I've separated this class from the other PR because of the slightly different implementation between .NET and .NET Framework. When the .NET Framework code performs encryption, generates signatures and validates signatures, it references the PrivateKey property and casts it to an RSACryptoServiceProvider. The .NET code uses the GetRSAPrivateKey() method and works with the RSA base class instead. This means that the unmerged .NET Framework code can't use certificates with CNG keys; the post-merge implementation will be able to do so.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.66%. Comparing base (5cb73fd) to head (a81eb63).

❗ Current head a81eb63 differs from pull request most recent head 5dfaecf

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2521      +/-   ##
==========================================
- Coverage   72.80%   72.66%   -0.14%     
==========================================
  Files         311      310       -1     
  Lines       61709    61547     -162     
==========================================
- Hits        44925    44724     -201     
- Misses      16784    16823      +39     

Flag	Coverage Δ
addons	92.88% <ø> (ø)
netcore	77.09% <100.00%> (-0.09%)	⬇️
netfx	70.38% <100.00%> (-0.07%)	⬇️

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[JRahnama]

Thank you @edwardneal. This looks good as it is.

Just a minor request, while you are working on this, is it possible to address the warnings on SqlColumnEncryptionCertificateStoreProvider.Windows class?

Constant names have name rule violation and instead of var can you change them to use explicit type or some others such as changing Int16 to short please or that needs a different PR for a different purpose?

[edwardneal]

Thanks @JRahnama. The coding style changes were small enough that they don't leave the diff looking unreadable; I've rolled them into this PR for simplicity's sake.

[saurabh500]

@David-Engel @JRahnama I think this is OK to merge. CI is green, no merge conflicts. Changes look good.