Remove EnableConnectionLevelAttributes option

[alanwest]

The attributes gated by EnableConnectionLevelAttributes are required. No other language has offered an option to disable these attributes. Removing EnableConnectionLevelAttributes to simplify things.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.38%. Comparing base (71655ce) to head (17ae4ee).
Report is 650 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2414       +/-   ##
===========================================
+ Coverage   73.91%   88.38%   +14.46%     
===========================================
  Files         267        9      -258     
  Lines        9615      439     -9176     
===========================================
- Hits         7107      388     -6719     
+ Misses       2508       51     -2457     

Flag	Coverage Δ
unittests-Instrumentation.SqlClient	88.38% <100.00%> (?)

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

Files with missing lines	Coverage Δ
...qlClient/Implementation/SqlActivitySourceHelper.cs	90.16% <100.00%> (ø)
....SqlClient/SqlClientTraceInstrumentationOptions.cs	100.00% <ø> (ø)

... and 270 files with indirect coverage changes

[rajkumar-rangaraj]

LGTM