tests: use packaging from setuptools instead of deprecated distutils
When invoking StrictVersion in 3.12 we got:
DeprecationWarning: distutils Version classes are deprecated. Use packaging.version instead.
distutils is dead in the standard library, and we have to move towards using
`setuptools` as general extern dependency. Instead of also requiring the extern
`packaging`, we will just use the packaging that is vendored in setuptools.
#if no-windows
$ mkdir -p xdgconf/hg
$ echo '[ui]' > xdgconf/hg/hgrc
$ echo 'username = foobar' >> xdgconf/hg/hgrc
$ XDG_CONFIG_HOME="`pwd`/xdgconf" ; export XDG_CONFIG_HOME
$ unset HGRCPATH
$ hg config ui.username 2>/dev/null
foobar
#endif