Create new analyzer to check for the correct usage of modal dialogs

[merriemcgaw]

This is one place where it is common to see application memory leak.

[KlausLoeffelmann]

Moving this to .NET 10 Future.
Due to recent events, I need to take over some other, higher priority tasks first, so, this will cannot be Preview 5, but I am still aiming for .NET 10, since this a MAJOR for reason for a lot of memory leaks in WinForms apps.

@merriemcgaw FYI.