Cleanup | SNI Native Wrapper

[benrr101]

This is a replacement of #3056 that will give us the complete CI

Description: This is a followup to the SNI Native Wrapper code merge. Each commit in this PR is an atomic change, so if the PR gets too cluttered to review all up, it can be stepped through one commit at a time. Most of these changes are just renaming and moving code around. One larger change is removing a bunch of private methods that were no longer necessary after extracting the DLL imports (as mentioned by @edwardneal).

Testing: There aren't really any functional changes here, so CI pass should be sufficient validation.

[benrr101]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov]

Codecov Report

Attention: Patch coverage is 92.06349% with 15 lines in your changes missing coverage. Please review.

Project coverage is 72.52%. Comparing base (87b5435) to head (ac9be84).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...Client/src/Interop/Windows/Sni/SniNativeWrapper.cs	95.41%	5 Missing ⚠️
...ient/src/Microsoft/Data/SqlClient/SqlDependency.cs	75.00%	4 Missing ⚠️
...osoft/Data/SqlClient/LocalDb/LocalDbApi.Windows.cs	0.00%	2 Missing ⚠️
...Data/SqlClient/TdsParserStateObject.Multiplexer.cs	0.00%	2 Missing ⚠️
...nt/netfx/src/Microsoft/Data/SqlClient/TdsParser.cs	87.50%	1 Missing ⚠️
...ft/Data/Sql/SqlDataSourceEnumeratorNativeHelper.cs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## main #3156 +/- ##
==========================================
- Coverage 72.57% 72.52% -0.05% 
==========================================
Files 288 289 +1 Lines 59526 59503 -23 ==========================================
- Hits 43201 43156 -45 - Misses 16325 16347 +22 

Flag	Coverage Δ
addons	92.58% <ø> (ø)
netcore	75.08% <90.29%> (-0.01%)	⬇️
netfx	71.16% <91.71%> (-0.06%)	⬇️

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