uv-resolver: normalize marker expressions (#4017)
This is a quick fix for some flaky tests where the output in the lock
file isn't stable because marker expressions can be combined in a
non-deterministic order.
I believe there is ongoing work to simplify marker expressions which
will help here, but I think some kind of normalization is still
ultimately needed to guarantee consistent output.
I first noticed the flaky test in:
https://github.com/astral-sh/uv/pull/4015
