tests: Add `--rhg` and `--with-rhg=<path>` options for `run-tests.py`
They are mostly equivalent to the corresponding `chg` options.
For now, many tests are still failing in this configuration.
It is *not* run on CI.
Differential Revision: https://phab.mercurial-scm.org/D10095
$ hg init
$ echo a > a
$ hg ci -Am t
adding a
$ hg mv a b
$ hg ci -Am t1
$ hg debugrename b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3
$ hg mv b a
$ hg ci -Am t2
$ hg debugrename a
a renamed from b:37d9b5d994eab34eda9c16b195ace52c7b129980
$ hg debugrename --rev 1 b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3