Assume option_channel_type

[carlaKC]

As outlined in lightning/bolts#1232, this feature bit has been deployed for along time and can be assumed.

Require Feature Bit

• Flip the feature bit to required in provided_init_features to start advertising the feature as required.

Assume Feature Bit

• Stop advertising the feature bit
• Fail channel negotiation if channel_type is not set

[carlaKC]

@elnosh was interested in picking this up, I'll be first reviewer.

@TheBlueMatt do you want to go straight to assuming the feature, or should we first flip it to required and get that into a release?