Install the integration test trace listener in Roslyn OOP

Fix MEF usage in several tests

Improvements to change signature / add parameter accessibility

Also check that Enum.HasFlag is a method

* Update dependencies from https://github.com/dotnet/roslyn build 20200420.1

- Microsoft.Net.Compilers.Toolset: 3.7.0-1.20210.7 -> 3.7.0-1.20220.1

* Update dependencies from https://github.com/dotnet/roslyn build 20200426.3

- Microsoft.Net.Compilers.Toolset: 3.7.0-1.20210.7 -> 3.7.0-1.20226.3

* Update dependencies from https://github.com/dotnet/roslyn build 20200504.1

- Microsoft.Net.Compilers.Toolset: 3.7.0-1.20210.7 -> 3.7.0-1.20254.1
Co-authored-by: Ndotnet-maestro[bot] <dotnet-maestro[bot]@users.noreply.github.com>

Convert RemoveUnnecessaryImportsTests to the new test framework

* Remove direct usage of Connection

* Refactor connection pooling

* SolutionChecksumUpdater

* GlobalNotificationRemoteDeliveryService

Disallow generating IEquatable for Ref Struct

Merge release/dev16.7-preview1 to master

Simplification and cleanup of our symbol index now that it is OOP.

Fix command name

Merge release/dev16.6 to release/dev16.7-preview1

Merge release/dev16.7-preview1 to master

Rename Non-Backtracking-Grouping to Atomic-Grouping

Only precompute and cache indices in the OOP process.

Fix crash in DeclarationNameProvider