patch files for PyQt6 compatibility

[kif]

Other minor change: perform relative imports instead of absolute imports.

[kif]

Validated PyQt5, PyQt6 and PySide6 on linux

[t20100]

I don't understand the need for patch_exec.
exec should be supported by PyQt6, PySide6 and PyQt5. With which binding/version you don't have it?

[kif]

@EdgarGF93 could you provide those details ?

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[kif]

@t20100: On the one hand, you are right, it works with exec() even under PyQt5, but not under PyQt6 where there are issues with exec_() (and other ...).

As first stage, I will replace all exec_() with exec() and then seek your help to fix PyQt6.

[t20100]

With which version of pyqt6 do you have the problem?

[kif]

I think I will merge this PR but not close the issue ... since it does not address it