Delays and timeouts based on block numbers

[muharem]

It would be really helpful if we could set up delays and timeouts based on block numbers.
On a different test actions like extrinsic sent, extrinsic in block, events received and asserts, etc, we can record the block number and control the delays.
This should make the tests more stable and less flaky. And not dependent on runtime timing setups.
It will also help to set the delays more accrued and speed up the tests execution.

[NachoPal]

It is a good idea, but it gets too complex when having many chains involved. The delay would be based on what's chain's block number?