Stay on the STA thread when launching instances of Visual Studio

This change ensures tests stay on the main thread, which has the COM message
filter installed that deals with certain IPC delays. DTE operations from
other threads are not able to gracefully recover from certain failure
conditions.

src/VisualStudio/IntegrationTest/TestUtilities/VisualStudioInstanceFactory.cs

@@ -109,7 +109,7 @@ public async Task<VisualStudioInstanceContext> GetNewOrUsedInstanceAsync(Immutab
             try
             {
                 bool shouldStartNewInstance = ShouldStartNewInstance(requiredPackageIds);
-                await UpdateCurrentlyRunningInstanceAsync(requiredPackageIds, shouldStartNewInstance).ConfigureAwait(false);
+                await UpdateCurrentlyRunningInstanceAsync(requiredPackageIds, shouldStartNewInstance).ConfigureAwait(true);
 
                 return new VisualStudioInstanceContext(_currentlyRunningInstance, this);
             }
@@ -170,7 +170,7 @@ private async Task UpdateCurrentlyRunningInstanceAsync(ImmutableHashSet<string>
                 }
 
                 // We wait until the DTE instance is up before we're good
-                dte = await IntegrationHelper.WaitForNotNullAsync(() => IntegrationHelper.TryLocateDteForProcess(hostProcess)).ConfigureAwait(false);
+                dte = await IntegrationHelper.WaitForNotNullAsync(() => IntegrationHelper.TryLocateDteForProcess(hostProcess)).ConfigureAwait(true);
             }
             else
             {
@@ -184,7 +184,7 @@ private async Task UpdateCurrentlyRunningInstanceAsync(ImmutableHashSet<string>
                 Debug.Assert(_currentlyRunningInstance != null);
 
                 hostProcess = _currentlyRunningInstance.HostProcess;
-                dte = await IntegrationHelper.WaitForNotNullAsync(() => IntegrationHelper.TryLocateDteForProcess(hostProcess)).ConfigureAwait(false);
+                dte = await IntegrationHelper.WaitForNotNullAsync(() => IntegrationHelper.TryLocateDteForProcess(hostProcess)).ConfigureAwait(true);
                 supportedPackageIds = _currentlyRunningInstance.SupportedPackageIds;
                 installationPath = _currentlyRunningInstance.InstallationPath;