[feature]: Implement Quiescence

[ProofOfKeags]

This issue tracks implementing Quiescence (stfu).

We need to implement this as a prerequisite for Dynamic Commitments (#7878). This issue will track the design approach.

[ProofOfKeags]

Here's a proposed plan of action (seeking approach ACK):

• Implement the wire message
• Implement a very simple state machine to handle the exchange of stfu messages
• Put the state machine inside the channelLink
• Make link ineligible for forwards when quiescent
• Fail downstream packet adds when quiescent
• Reset the state machine when the peer disconnects
• Handle invalid upstream adds/fulfills/fails by recycling the connection
• Add feature bits

[Roasbeef]

Reset the state machine when the peer disconnects

As is, I think you'll sorta get this "for free", as if it lives as a sub-component of the link, then it'll be torn down and re-created once the connection is re-established.

[ProofOfKeags]

🥹