Modules: add FindLua.cmake

This is a version agnostic variant of FindLua50.cmake and FindLua51.cmake.
Merge topic 'FindLua' into next

89cfa20 Modules: add FindLua.cmake
FindPython*: simplify version selection

CMake already provides the version components split into variables, no need to
split them again.
Merge topic 'FindPython_versions' into next

afd4f7f FindPython*: simplify version selection