...so we can have multiple just in time channels with the same lsp.
We already save a remote scid alias in `on_channel_ready` which we
already have received after the new zeroconf channel is in open state.
So setting the alias to the static node id hash is counterproductive
because it doesn't allow to differentiate between channels.
Also extends the regtest (`just_in_time`) to do a second channel
opening, to cover this scenario. This doesn't add much runtime to
the test, so the cost seems reasonable.
f321x
f56e1cafac