Send mined transaction IDs to the download and verify task for cancellation

[teor2345]

Motivation

Zebra needs to remove mined transaction IDs from the mempool download and verify tasks.

Design

Tasks can await tip changes using ChainTipChange::tip_change and TipAction::Grow:

zebra/zebra-state/src/service/chain_tip.rs

Line 313 in 44ac067

pub async fn tip_change(&mut self) -> Result<TipAction, watch::error::RecvError> {

[mpguerra]

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