No overflow button for toolbars and sidebars in case window is small

Description

When you have a low screen resolution or drag the PCB editor smaller, the toolbar at the top and the two button bars on both sides can't display all the controls anymore. Most programs then display an overflow menu button that contains the remaining items, but Kicad doesn't.

Steps to reproduce

1. Drag the PCB editor window small enough that eg. the insert bitmap button vanishes
2. Try to click the insert bitmap button
3. ???

KiCad Version

Application: KiCad PCB Editor x86_64 on x86_64

Version: 7.0.0-1.fc37, release build

Libraries:
	wxWidgets 3.2.1
	FreeType 2.12.1
	HarfBuzz 5.2.0
	FontConfig 2.14.1

Platform: Fedora release 37 (Thirty Seven), 64 bit, Little endian, wxGTK, gnome-xorg, x11

	wxWidgets: 3.2.1 (wchar_t,wx containers) GTK+ 3.24
	Boost: 1.78.0
	OCC: 7.6.3
	Curl: 7.85.0
	ngspice: 38
	Compiler: GCC 12.2.1 with C++ ABI 1017

Build settings:
	KICAD_SPICE=ON