Fix: Signers CI tests and refresh signer config behaviors

[kantai]

Fix: a handful of issues causing timing-related test failures in CI

• make not_available_try_again error in GetStackers, and make it transient in the signer binary
• make signer binary timeout on retries in client
• update signer outer runloop to differentiate between 'not in signer set' and 'have not loaded info yet'
• update signer outer runloop to handle errors and non-presence differently in the signer config refresh
• update signer outer runloop to perform signer config refresh on the current cycle (if not loaded yet) and on the next cycle (if in prepare phase for the next cycle). This was causing an issue on exactly the first cycle of Nakamoto, because the signer set cannot be loaded for the first cycle until after the prepare phase
• update the signer outer runloop to check the node’s block height on event receipt as well
• update the testing harnesses to wait and check more appropriately for status checks from signers, etc.

[kantai]

Look at all those green checks!

[jcnelson]

Went ahead and merged -- need this for #5040

[kantai]

Okay -- I have a new test I'm about to add which covers the changeset, then I'll re-add to queue.

[kantai]

It looks like there's still an intermittent failure in the multiple_miners test -- it looked like a bind failure, though, which means it should be an easy fix. Will do in a separate PR, though.

[blockstack-devops]

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