FindPythonLibs: Find consistent Python interp, headers, libs (#13794)

When possible, get consistent version of the Python interpreter, headers path,
and library.

Now find_package(PythonLibs) internally calls find_package(PythonInterp
QUIET) and uses the resulting PYTHON_VERSION_MAJOR and
PYTHON_VERSION_MINOR to prefer these versions when looking for the
header path and library.  The Python_ADDITIONAL_VERSIONS variable has
priority over the interpreter version.

Co-Author: Adam Wolf
Co-Author: Gert Wollny <gw.fossdev@gmail.com>
Merge topic 'different-python-header-libs-exe-0013794' into next

3816cd2d FindPythonLibs: Find consistent Python interp, headers, libs (#13794)