Remove SQL 2000 client-side debugging support

[edwardneal]

Follows up #2940, removing the client-side support for SQL 2000's debugging mechanisms from netfx and aligning with netcore.

The SqlConnection diff will be easier to parse with whitespace changes disabled. I've removed the methods which enable the now-defunct debugging, the SqlDebugContext class and MEMMAP struct which they use and the PInvokes they reference. These PInvokes were the only thing in netfx\src\Microsoft\Data\Common\NativeMethods.cs, so I've deleted the file.

This isn't critical for preview3.

/cc @benrr101 - there's no need to port PInvokes from NativeMethods.cs anywhere. It's the same story for the SafeNativeMethods.cs file in the same folder.

[benrr101]

Uhhhhhhhhhhhhhhhhhhhhhhhhhhh 😅
Can I get my PR in first and you can delete whatever from it that is no longer needed?

[edwardneal]

No worries - I'll just merge back into my branch once #2997 is done.
Edit: done!

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 16 lines in your changes missing coverage. Please review.

Project coverage is 72.56%. Comparing base (4052186) to head (3aeec6f).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
...etfx/src/Microsoft/Data/SqlClient/SqlConnection.cs	50.00%	16 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2981      +/-   ##
==========================================
+ Coverage   72.48%   72.56%   +0.07%     
==========================================
  Files         288      288              
  Lines       59493    59385     -108     
==========================================
- Hits        43123    43091      -32     
+ Misses      16370    16294      -76     

Flag	Coverage Δ
addons	92.58% <ø> (ø)
netcore	75.36% <ø> (-0.07%)	⬇️
netfx	71.09% <50.00%> (+0.16%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[benrr101]

Let's gooooooooo delete that code!

[MichelZ]

#2839 next! :)