Add a zebrad acceptance test that does a full sync to tip

[teor2345]

Motivation

This is the Rust part of:

• Run full sync tests on Mainnet #1592

Suggested Design

Here's one way to do the Rust part of this change:

Partly done in #3495:

1. Create a future that returns when the estimated height has been reached
2. Add that future to zebrad start's main loop as a "continuing task", so Zebra exits when it finishes

New work:
3. Create a sync test case with a 6 hour timeout, which uses a "stop at estimated height" config

zebra/zebrad/src/commands/start.rs

Lines 195 to 200 in 1a14baf

	// Wait for tasks to finish
	let exit_status = loop {
	let mut exit_when_task_finishes = true;
	let result = select! {
	sync_result = &mut syncer_task_handle => sync_result

Originally posted by @teor2345 in #1592 (comment)

Follow-Up Tasks

Required:

• check that we are at least 200^* blocks above the highest checkpoint (detects stalls)

^* I picked 200 because 100 non-finalized blocks are excluded from checkpoint generation, and it takes 2 hours to build and run the test. (If mainnet syncs get fast, or we're using testnet.) If we make it any higher, the first time we submit each checkpoint update PR the tests will be slow, because we'll wait to sync newly generated blocks.

Useful to increase coverage:

• wait until the mempool has been active for a few minutes before exiting (increases coverage)

Optional:

Only if needed due to CI failures:

• Adjust the timeout so that at least 99% of syncs succeed (makes failing tests fail faster)

Here is a refactor I don't think we need to do yet:

• Move debug stop at height to the zebrad start main loop #3442 (simplifies similar test code that's currently in the state)

[teor2345]

I just realised that the estimate logging PR does some of this stuff already:

• Chain Tip Estimate Test: Log chain progress while Zebra is syncing #3495

Turns out logging estimates in a helpful way is similar to using them to stop Zebra.