bolt-simple-taproot: taprooty level 1

In this extension BOLT, we specify the initial flavor of taproot
channels to be deployed. This channel type uses musig2 aggregated keys
and signatures for the funding output, making it a normal single
signature key path spend. All outputs are then updated to use P2T2
(segwit v1) outputs. The coop close process has been simplified to
always terminate, and the co-op close transaction now also flags RBF to
make way for future schemes that enable the process to be restarted
which enables co-op close fee bumping.

A top-level key spend output is used to the revocation of HTLC outputs.
The revocation for the local output uses a script path to ensure that
information needed to sweep the anchors by 3rd parties is always
revealed on chain.

Author: Roasbeef