Improve fee sniping deterrence [BIP326]

[ValuedMammal]

Description

First attempt at bip326

for reference: BIP326 Bitcoin Core Sparrow

Notes to the reviewers

Changelog notice

Checklists

All Submissions:

• [x] I've signed all my commits
• [x] I followed the contribution guidelines
• [x] I ran cargo fmt and cargo clippy before committing

closes #1134

[LLFourn]

@ValuedMammal since lightning doesn't us taproot yet is there a strong motivation for doing this now? I do think the goal of this is admirable and I think implementing it as the default as part of a bdk_tx_builder crate would make it cleaner (where we'd drop the policy stuff in favor of the miniscript planning module).

[notmandatory]

I propose we push to to a post 1.0 release since it's a functional improvement that shouldn't change the current wallet API.