refactor: bls_aggr encapsulate task initialization params in TaskMetadata

[damiramirez]

What Changed?

This PR introduces a refactor in task initialization by encapsulating related parameters into a new struct and simplifying function interfaces.

• Create a new struct TaskMetadata with a constructor TaskMetadata::new to initialize a new task and with_window_duration to set the window duration.
• initialize_new_task and single_task_aggregator accept TaskMetadata instead of multiple params.
• Removed initialize_new_task_with_window.

pub struct TaskMetadata {
    task_index: TaskIndex,
    task_created_block: u32,
    quorum_numbers: Vec<u8>,
    quorum_threshold_percentages: QuorumThresholdPercentages,
    time_to_expiry: Duration,
    window_duration: Duration,
}

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]

Left some minor comments

[MegaRedHand]

We should have before and after examples here. One for initialize_new_task and another with initialize_new_task_with_window

[damiramirez]

Done 7730ed1! What do you think about the format?

[MegaRedHand]

The "before" and "after" don't render correctly in markdown. We could have them as code comments instead

[MegaRedHand]

Really good format otherwise!