In preparation for Gossip 1.75, we add new TLV's to the `ChannelReady`
message. Namely: `AnnouncementBitcoinNonce` and `AnnouncementNodeNonce`.
These will be used to exchange nones required for producing the partial
signature to be send in the `AnnouncementSignatures2` message.
The type numbers for these new fields are even because if they are set,
then a peer is expecting its peer to understand gossip 1.75 and the new
fields.
In this commit, we update new Taproot related TLVs (nonces, partial sig,
sig with nonce, etc). Along the way we were able to get rid of some
boiler plate, but most importantly, we're able to better protect against
API misuse (using a nonce that isn't initialized, etc) with the new
options API. In some areas this introduces a bit of extra boiler plate,
and where applicable I used some new helper functions to help cut down
on the noise.
Note to reviewers: this is done as a single commit, as changing the API
breaks all callers, so if we want things to compile it needs to be in a
wumbo commit.
