Remove thread requirement from CodeAnalysisDiagnosticAnalyzerService

This looks to be safely callable from any thread.

Author: jasonmalinowski

src/Features/Core/Portable/Diagnostics/CodeAnalysisDiagnosticAnalyzerService.cs

@@ -50,9 +50,7 @@ public CodeAnalysisDiagnosticAnalyzerService(
             _workspace = workspace;
             _diagnosticAnalyzerService = _workspace.Services.GetRequiredService<IDiagnosticAnalyzerService>();
 
-            // Main thread as OnWorkspaceChanged's call to IDiagnosticAnalyzerService.RequestDiagnosticRefresh isn't clear on
-            // threading requirements
-            _ = workspace.RegisterWorkspaceChangedHandler(OnWorkspaceChanged, WorkspaceEventOptions.RequiresMainThreadOptions);
+            _ = workspace.RegisterWorkspaceChangedHandler(OnWorkspaceChanged);
         }
 
         private void OnWorkspaceChanged(WorkspaceChangeEventArgs e)

src/Features/Core/Portable/Diagnostics/IDiagnosticAnalyzerService.cs

@@ -22,6 +22,9 @@ internal interface IDiagnosticAnalyzerService : IWorkspaceService
     /// <summary>
     /// Re-analyze all projects and documents.  This will cause an LSP diagnostic refresh request to be sent.
     /// </summary>
+    /// <remarks>
+    /// This implementation must be safe to call on any thread.
+    /// </remarks>
     void RequestDiagnosticRefresh();
 
     /// <summary>