[ Fix and Re-enable ] Diagnostic Area - Feature Tests

The following tests were disabled while open-sourcing the test area

- [ ] XamlSourceInfoTest_ReleaseBaml_Enabled
- [ ] XamlSourceInfoTest_DebugSystemResources
- [ ] XamlSourceInfoTest_DebugBaml_Enabled
- [ ] XamlSourceInfoTest_LocalXaml_Enabled
- [ ] XamlSourceInfoTest_XamlWithUri_Enabled
- [ ] [Microsoft.Test.Discovery.Test(1, "ResourceDictionaryDiagnostics", TestParameters="Mode=Enable")]

The cause of failure is not known as of now. It may be that the tests themselves need to be fixed.

**For re-enabling the tests -**
1. Search for the above in the code.
2. Uncomment the attribute before the test function.

To run the tests in isolation, use the following command
```
.\RunTests.cmd /Area=Diagnostic /Name=
```

For debugging the tests, add the `/DebugTests` argument in the command above.