In this commit, we split off the protocol options into a normal and
legacy sub-config. The legacy sub-config protected by a built tag, and
will only be populated if thet tag is set. Legacy options now have a
`legacy` prefix. So `--protocol.legacyonion` is now `--protocol.onion`,
and `--protocol.committweak`, is now `--protocol.legacy.committweak`.
We also create a new experimental protocol feature sub-config for newer
features that may not yet been fully complete, so they require a build
tag.
In this commit, we add a new legacy protocol command line flag:
`committweak`. When set, this forces the node to NOT signal usage of the
new commitment format. This allows us to test that we're able to
properly establish channels with legacy nodes. Within the server, we'll
now gate our signalling of this new feature based on the legacy protocol
config. Finally, when accepting/initiating a new channel funding, we'll
now check both the local and remote global feature bits, only using the
new commitment format if both signal the global feature bit.
In this commit, we add a new build tag protected sub-config for legacy
protocol features. The goal of this addition is to be able to default to
new feature within lnd, but expose hooks at the config level to allow
integration tests to force the old behavior to ensure that we're able to
support both the old+new versions.
