feat: use `timeout` param from burnchain config

[obycode]

Just adding documentation about the burnchain.timeout config parameter and then using it instead of a 60s hard-coded value.

[obycode]

I will check these failing integration tests before merging.

[obycode]

• tests::epoch_25::microblocks_disabled is flaky in CI but passes locally
• tests::nakamoto_integrations::forked_tenure_is_ignored is flaky in CI but passes locally
• tests::signer::v0::multiple_miners is flaky in CI but passes locally
• tests::signer::v0::mine_2_nakamoto_reward_cycles is hitting some strange CI problem, but passes locally (it takes almost 5 minutes locally, so that's likely too long to run in CI)
• tests::signer::v0::signer_set_rollover is hitting some strange CI problem, but passes locally

[blockstack-devops]

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