Unify the pattern used to run a feature in OOP

[tmat]

Unifies the pattern used to run a feature in OOP and applies nullable annotations.

This reflects the fact that the remote call may fail and return null, which previously wasn't consistently handled across all features. If it happens we should fall back to running in-proc.

FeatureEntryPoint()
{
  var client = await RemoteHostClient.TryGetClient();
  if (client != null) { var result = client.RemoteCall(); if (result.HasValue) return result.Value; } 
  FeatureImplInProc(); 
}

Also reduces the amount of overloads and turns extension methods used for remote invocation into instance methods defined directly on RemoteHostClient type.

[CyrusNajmabadi]

comment

[CyrusNajmabadi]

comment.

[tmat]

@dotnet/roslyn-ide PTAL

[ryzngard]

Looks reasonable to me

[CyrusNajmabadi]

c

[CyrusNajmabadi]

Regardless, we should likely take the conversation about enforced styles to some other more suitable location.

[sharwell]

Done with 29/43 files

[CyrusNajmabadi]

Small concerns. Nothing major though.

[JoeRobich]

All checks have passed. Overriding to merge.