Add tests for System.Diagnostics.Process.Responding

[eiriktsarpalis]

#38385 added a test for Process.Responding, which however was disabled since it depends on the current implementation characteristics of Wordpad.

We should replace it with a test that consistently reproduces the behaviour.

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[adamsitnik]

Wordpad

@eiriktsarpalis did you mean notepad?

runtime/src/libraries/System.Diagnostics.Process/tests/ProcessTests.cs

Lines 1598 to 1600 in 021e776

	public void MainWindowTitle_GetWithGui_ShouldRefresh_Windows()
	{
	const string ExePath = "notepad.exe";

[eiriktsarpalis]

No, the PR referenced in #40703 relied on wordpad behaviour to produce a non-responsive process.

[adamsitnik]

@eiriktsarpalis thanks!

FWIW the commit that removed the test: c4d3ed5