urlutil: move url "fixing" at the time of `ui.paths` initialization

Authored by marmoute.


urlutil: move url "fixing" at the time of ui.paths initialization

Doing such fixing at the time is simpler and will be necessary to deal with
urls list in a sane manner. It also reduce the size of fix-config which is
always better.

I wish we could get ride of the hackish way to pass the root around, I suspect
that the root variable could be stored as part of the config value, along side
the source. However getting to the end of this root business is a far too
large detours to make now.

The test change to tests/test-hgrc.t and test-config.t are expectied since
we are not longer altering the config itself, but the way it is interpreted when
building path. This seems more correct.

I also added a couple of test call to test-config.t and test-globalopts.t to
clarify that the expanding process is properly happening a the right time.

Differential Revision: https://phab.mercurial-scm.org/D10451