fix: resolve the remote URI using url.*.insteadOf (#1394)

This change introduces a new method for resolving the URI for a given
remote (by name), ensuring that the URI is rewritten following the rules
defined in `url.*.insteadOf` configuration.

When `go-git@69aefb67315d775bf73df836b1e3ba5a3b321198` lands in a
release (and we update go-git to that release), this should be
refactored to use `config.URL.InsteadOfs()`, which supports multiple
`url.*.insteadOf` configuration blocks instead of the current limitation
of always taking the last definition.

Closes: #944
Change-Id: Iffd111a1f4c42eff12613dcbd1b0d27df415f5e8