addr: Attempt to learn our address with ORPort

If no Address statement are found in the configuration file, attempt to learn
our address by looking at the ORPort address if any. Specifying an address is
optional so if we can't find one, it is fine, we move on to the next discovery
mechanism.

Note that specifying a hostname on the ORPort is not yet supported at this
commit.

Closes #33236

Signed-off-by: David Goulet <dgoulet@torproject.org>