Activate Python scripting

[jmaibaum]

This PR activates Python 3 scripting, using wxPython Phoenix.

Note that this effectively also switches from wxWidgets 3.1.2 to the wxWidgets bundled with wxPython Phoenix 4.0.7.post2 as recommended by the wxPython docs. The bundled wxWidgets calls itself version 3.0.5.

[flathubbot]

Started test build 14700

[flathubbot]

Build 14700 successful
To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/14031/org.kicad_pcb.KiCad.flatpakref

[flathubbot]

Started test build 15519

[flathubbot]

Build 15519 successful
To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/14829/org.kicad_pcb.KiCad.flatpakref

[jmaibaum]

@Aydan It will be merged once one of the flathub maintainers finds time to review (and approve) these changes. It is out of my control, I am just proposing this change to the best of my knowledge.

[jmaibaum]

A quick progress report: I have tried to build against the newly released wxPython 4.1.0/wxWidgets 3.1.4, but apparently upstream KiCad is having an issue with the recent privateization of the wxPaintEvent constructor in the bundled wxWidgets version (see https://gitlab.com/kicad/code/kicad/-/issues/4168).

So, if this PR is intended to be merged before KiCad 5.1.7 is going to be out (might be quite a few months from now, 5.1.6 is still not released), it seems that we need to be sticking to wxPython 4.0.7.post2 as per this PR.

[flathubbot]

Started test build 20305

[flathubbot]

Build 20305 successful
To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/19474/org.kicad_pcb.KiCad.flatpakref

[flathubbot]

Started test build 20315

[flathubbot]

Build 20315 successful
To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/19482/org.kicad_pcb.KiCad.flatpakref

[flathubbot]

Started test build 20410

[flathubbot]

Build 20410 successful
To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/19570/org.kicad_pcb.KiCad.flatpakref