Behaviour of resizable is different across platforms

[sourcebox]

When setting window.set_resizable(false) the window is still resizable via window.set_inner_size() on macOS and Windows, but not on Linux. I would expect that window.set_resizable(false) just disables the manual handles for the mouse on all platforms but keep it possible to change the size from the application itself.

[kchibisov]

I think it makes sense to allow setting size manually with resizable false.

I'll try sending patch for X11/Wayland and update docs wrt that when I have time, should be pretty simple from what I can see.