refactor: bls_aggr encapsulate parameters into TaskSignature

[damiramirez]

What Changed?

This PR refactors the process_new_signature function by encapsulating related parameters into a new struct called TaskSignature.

• Create TaskSignature struct with a constructor method.
• process_new_signature now accepts a TaskSignature instead of separate parameters.
• Update CHANGELOG.md

pub struct TaskSignature {
    task_index: TaskIndex,
    task_response_digest: TaskResponseDigest,
    bls_signature: Signature,
    operator_id: FixedBytes<32>,
}

Reviewer Checklist

• New features are tested and documented
• PR updates the changelog with a description of changes
• PR has one of the changelog-X labels (if applies)
• Code deprecates any old functionality before removing it

[MegaRedHand]

Please sync with dev and update the changelog

[MegaRedHand]

LGTM