Add block-based waiting for /poll, /listen, /spv endpoints

[LindaOrtega]

I'm creating this issue as a way to discuss the following problem:

As I'm working with the integration tests and devnet, I am having to wait a bit for blocks to come in since devnet is not as fast in producing "blocks" as pact-server.

In the code I'm setting a couple of sleep timers for some arbitrary time. This is a point of indeterminism.
I've seen this when working with /poll, /listen, and /spv endpoints.

A helper function that can be given one of the api fetch functions and that utilizes both a time-based and a block-based exponential backoff would be useful in this situation.

[LindaOrtega]

If the /spv endpoint is queried too soon, you'll see the following error:

SPV target not reachable: target chain not reachable. Chainweb instance is too young

It seems that you have to wait about 3 cut heights (sometimes a little more) between when you submit the cross-chain transaction and when you query the spv endpoint.

Update:
In worst case it is 6 block heights (module off-by one errors).
Assume that the target chain was lagging behind when the the burn happens on the source. In worst case it would take 3 blocks for the target chain to get to the block height at which the burn occurred and another 3 blocks until the proof becomes available.

[LindaOrtega]

Wrapping /listen and /spv in an exponential-backoff function worked for fixing the inconsistency with the integration-tests on devnet. But we might still want to explore a more tailored approach for this issue.

From conversation with @mightybyte:

Potential place of inspiration for how often to query: https://en.wikipedia.org/wiki/Cycle_per_second
Also, across testnet and mainnet (and potentially devnet) and for a given chain, a user can expect an average of 1 block every 30 seconds.
Consequently, users should expect the overall cut height to increase by 20 (the total number of chains currently in the network) every 30 seconds.

[github-actions]

This issue is stale because it is open for 60 days with no activity