Clear release requests when a bitcoin lock burns

[blakebyrnes]

What changed

• clear the pending release request when a bitcoin lock burns so the pending cosign state is removed too
• cover the spent and expiration paths in the existing bitcoin lock tests

Testing

• cargo test -p pallet-bitcoin-locks --lib

[Copilot]

Pull request overview

This PR ensures that when a Bitcoin lock is burned (due to expiration or being spent), any pending release request is cleared so associated “pending cosign” tracking is also removed, and it extends existing tests to cover these burn paths.

Changes:

• Clear LockReleaseRequestsByUtxoId (and related cosign tracking) during burn_bitcoin_lock.
• Extend expiration and “spent” tests to create a pending release request and assert the pending cosign state is removed when the lock burns.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
pallets/bitcoin_locks/src/lib.rs	Clears pending release requests during lock burn via take_release_request.
pallets/bitcoin_locks/src/tests.rs	Adds coverage for expiration/spent burn paths with a pending release request and checks storage cleanup.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

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