Update packaging for 4.3

TODO

• Investigate what can still be unvendored
  • clipper2
  • msdfgen
  • glslang
  • rvo2_2d
  • rvo2_3d
  • xatlas
• Forward other patches upstream
  • wslay compiler flags (not needed, Debian-specific)
  • removing default executable suffix (https://github.com/godotengine/godot/pull/101403)
• Split large "Update packaging for new upstream release" commit into smaller, more reviewable, ones
  • Rename and change content of patches in two separate commits (!3 (comment 569117))
• undo namespacing so src:godot always tracks latest version