Enable debugging/EnC integration tests

This PR disables integration tests: https://github.com/dotnet/roslyn/pull/34027, because it requires the <s>lab/16.2stg</s> 16.10 build with VS debugger insertion which won't be available on the CI machine.

Enable the tests again once the CI machine is upgraded.

Also uncomment `#if TODO` in `WaitForDesignMode` 