upstreaming wxwidgets

[Ckath]

currently wxwidgets is obtained from https://github.com/audacity/wxwidgets, it'd be far better if this was just upstream wxwidgets or at least a sneed owned fork.
on first inspection the two dont seem to differ much but just swapping them out instantly runs into some issues, see the wxwidgets branch for more.

still not sure if it'll be possible to upstream entirely or if a fork is needed, but we'll find out.

opened after conan was pretty much gone as successor of #47

[Ckath]

seems its not that bad, just messing around it builds with upstream v3.1.5, as is. without too many issues besides the appimage ci generates being broken and it not working out yet on windows (which might also be my cmake files)

probably ideal to get it going with v3.0.5 since distros ship with that, but for the 'just lock it at some commit with a submodule' approach there might be hope for v3.1.5

[Ckath]

as for the non distro supplied option and just going with a newer wxwidgets:
the build with 3.1.3 (which the audacity fork is based on), 3.1.4 and 3.1.5 all end in segfault on appimage launch, for me anyway. though they all run built locally. I'm not sure if anyone tested the mac builds. windows fails on some linking error I'm not sure I can easily solve without a windows system.

on second thought I'm also not really fond of patching in 3.0.5 compatability either with how far behind upstream that is, unless its ensured distros will stay on that for ages to come.

[ImGonnaChuck]

To even begin to work on this we need to know and document the differences between the stock and the modified versions of the library.