Merge | SNI Wrapper Class Extraction

[benrr101]

Description: Finally we're moving onto merging the SNI wrapper class. The strategy for merging this class is to

1. Extract classes/enums from the main class into separate files. (this PR)
2. Create an interface for native method providers and switch which implementation is used based on platform (next PR, ready to go)
3. Merge remaining code (PR after that)

This PR reduces the bulk of the code in the netcore SNINativeMethodWrapper class, making merging much easier.

Testing: This is another PR where code is just moving around, not changing functionality. As such, the pipeline build should verify it.

[codecov]

Codecov Report

Attention: Patch coverage is 87.27273% with 7 lines in your changes missing coverage. Please review.

Project coverage is 72.69%. Comparing base (a6f9ce3) to head (5d6ee99).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
....SqlClient/src/Microsoft/Data/SqlClient/SqlUtil.cs	0.00%	3 Missing ⚠️
...src/Microsoft/Data/SqlClient/LocalDBAPI.Windows.cs	0.00%	2 Missing ⚠️
...t/netfx/src/Microsoft/Data/SqlClient/LocalDBAPI.cs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3002      +/-   ##
==========================================
+ Coverage   72.44%   72.69%   +0.24%     
==========================================
  Files         288      285       -3     
  Lines       59493    59155     -338     
==========================================
- Hits        43102    43003      -99     
+ Misses      16391    16152     -239     

Flag	Coverage Δ
addons	92.58% <ø> (ø)
netcore	75.45% <81.25%> (+0.07%)	⬆️
netfx	71.09% <84.37%> (+0.18%)	⬆️

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