BIP431: Opt In Topologically Restricted Until Confirmation Transactions For More Robust Fee-bumping

This is a BIP for Topologically Restricted Until Confirmation (TRUC) Transactions. It's also called "v3 transaction policy" since the marker is nVersion=3.

A specification is useful for coordination between node impls that want to implement the same policy and applications that want to use it. For those that are not interested in the details of v3 policy, this also serves as a writeup of the specific pinning problems we aim to address. There has been discussion of using this in other protocol design and multiple requests for its documentation to exist in the BIPs repository, so I'm opening a PR here.

Implementation:

• https://github.com/bitcoin/bitcoin/pull/28948
• https://github.com/bitcoin/bitcoin/pull/29873
• https://github.com/bitcoin/bitcoin/pull/29496

Example usage and things built on top:

• Package RBF
  • https://github.com/bitcoin/bitcoin/pull/28984
• Ephemeral Anchors
  • https://github.com/bitcoin/bitcoin/pull/29001
  • https://github.com/bitcoin/bips/pull/1524
• LN commitment transactions
  • https://delvingbitcoin.org/t/lightning-transactions-with-v3-and-ephemeral-anchors/418
  • https://github.com/instagibbs/bolts/commits/zero_fee_commitment
• LN-Symmetry
  • https://delvingbitcoin.org/t/ln-symmetry-project-recap/359
  • https://github.com/instagibbs/lightning/tree/eltoo_support

Discussion and history:

• https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022-January/019817.html
• https://gist.github.com/glozow/25d9662c52453bd08b4b4b1d3783b9ff
• https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022-September/020937.html
• https://delvingbitcoin.org/t/v3-transaction-policy-for-anti-pinning/340
• https://github.com/bitcoin/bitcoin/pull/25038