Remove unused code files

[edwardneal]

Related to #1261, but doesn't merge anything.

There are a few code files which were merged in earlier PRs, but one of the copies was left in place. This PR just cleans these up so we have a clearer picture of the remaining merges.

• netcore/TdsParserStaticMethods: Add support for aliases on netcore+Windows #1588
• netfx/SqlBulkCopyColumnMapping: Merge more shared files #618
• netfx/SqlDependencyUtils: Move to Shared for SqlDependencyUtils.cs #1370

The other file is netfx/SqlGenericUtil. This class is referenced in the project, but not used anywhere.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.07%. Comparing base (6d33e9d) to head (5986e1a).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2814      +/-   ##
==========================================
+ Coverage   72.03%   72.07%   +0.03%     
==========================================
  Files         305      304       -1     
  Lines       61804    61801       -3     
==========================================
+ Hits        44522    44544      +22     
+ Misses      17282    17257      -25     

Flag	Coverage Δ
addons	92.90% <ø> (ø)
netcore	75.93% <ø> (+0.02%)	⬆️
netfx	70.26% <ø> (+0.06%)	⬆️

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[JRahnama]

@edwardneal, these PRs are crucial in achieving our goal of having a single .csproj file for both .NET Core and .NET Framework. We have already converted the .NET Framework project to the SDK-style format, and our next step is to consolidate both projects into a single .csproj file. Your efforts are really appreciated.

[edwardneal]

Thanks - it'll be good to see the merge completed, although I'm conscious that I've not touched the core TdsParser/SqlConnection/SqlCommand classes much yet. Hopefully we'll be able to enable some new functionality (such as Always Encrypted for SqlClient on Linux) along the way too.