refactor(chain)!: Update KeychainTxOutIndex methods to use owned K and ScriptBuf

[rustaceanrob]

Description

Make all method signatures of KeychainTxOutIndex take owned K and use ScriptBuf instead of its borrowed counterpart &Script. Fixes #1482

Notes to the reviewers

Steve also added a CI fix as well

Changelog notice

• Make all method signatures of KeychainTxOutIndex take owned K
• Update KeychainTxOutIndex methods to use ScriptBuf

Checklists

All Submissions:

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

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[notmandatory]

I pushed commit to also update KeychainTxOutIndex to use owned ScriptBufs instead of &Scripts.

[notmandatory]

⛏️ @rustaceanrob one small thing, can you change your commit description to be a little more descriptive, something like:

refactor(chain)!: update KeychainTxOutIndex methods to use owned K

[notmandatory]

I added a commit to limit tests to 2 threads, this is what I've always had to do locally to fix an issue with bitcoind based tests making calls to quickly.

[storopoli]

I added a commit to limit tests to 2 threads, this is what I've always had to do locally to fix an issue with bitcoind based tests making calls to quickly.

Oh the nasty -- --test-threads=2 strikes back.
Yeah I had tons of issues with that in the past while prepping the Nix CI PR.

[notmandatory]

ACK ade5999

We should hold off on merging this until after PR for #1103 is merged so we don't disrupt that work. But may also require a re-base for this PR.

[ValuedMammal]

ACK ade5999

[notmandatory]

This needs to be rebased after #1514 is merged.

[notmandatory]

I pushed a test rebase, will do final rebase after #1514 is merged.