[feature]: require Channel Acceptor to be registered before accepting channels

[AndySchroder]

Channel Acceptor is a great tool to control what type of channels will be accepted. However, if no Channel Acceptor is registered, doesn't any channel get accepted? Seems to me like we should have a config flag on lnd to require at least one Channel Acceptor to be registered to the RPC before any channel will be accepted. Otherwise, you may have a situation on startup where a channel is accepted before the Channel Acceptor has time to register itself. Alternatively, if you have a bug in your Channel Acceptor and it crashes, you would want no channels to be accepted until that is fixed.

[Crypt-iQ]

Just a note that for zero-conf channels they will be auto-rejected unless an acceptor is present