… types

…chans

In this commit, we add support for the new musig2 channel funding flow.
This flow is identical to the existing flow, but not both sides need to
exchange local nonces up front, and then signatures sent are now partial
signatures instead of regular signatures.

The funding manager also gains some new state of the local nonces it
needs to generate in order to send the funding locked message, and also
process the funding locked message from the remote party.

In order to allow the funding manger to generate the nonces that need to
be applied to each channel, then AddNewChannel method has been modified
to accept a set of options that the peer will then use to bind the
nonces to a new channel.

… channels

In this commit, we start to set _internally_ a new feature bit in the
channel announcements we generate. As these taproot channels can only be
unadvertised, this will never actually leak to the public network. The
funding manager will then set this field to allow the router to properly
validate these channels.

In this commit, we update the chain watcher to be able to generate the
correct pkScript so it can register for confirmation and spend
notifications for taproot channels.

This ensures that when loading the channel again after a normal chan
reest, we generate the local nonces, which ensures we can then process
nonces the remote party sends us in their chan reest message.

This ensures that we end up playing the target output on chain for
taproot channels.