Release 22.0 of packaging module can no longer parse invalid Python version
number, an exception is now raised.

Conda loader used the keys of the packages dict as version numbers to sort,
which are in the form "<arch>/<version>-<build>", but those cannot be parsed
anymore.

So extract intrinsic version numbers of packages instead to sort the list of
versions.

Also update snapshot release names to "<version>-<build>-<arch>" as each
release for a given architecture targets a different directory.