fix: daemon: set real beacon schedule when importing chain

[arajasek]

Related Issues

#11041

Proposed Changes

• Unify the code that creates beacon schedules from drand config
• Actually set the beacon schedule when running import-chain

Additional Info

Syncs mainnet ✔️
Repro in #11041 no longer panics ✔️

Checklist

Before you mark the PR ready for review, please make sure that:

• Commits have a clear commit message.
• PR title is in the form of of <PR type>: <area>: <change being made>
  • example: fix: mempool: Introduce a cache for valid signatures
  • PR type: fix, feat, build, chore, ci, docs, perf, refactor, revert, style, test
  • area, e.g. api, chain, state, market, mempool, multisig, networking, paych, proving, sealing, wallet, deps
• New features have usage guidelines and / or documentation updates in
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  • Discussion Tutorials
• Tests exist for new functionality or change in behavior
• CI is green

[fridrik01]

LGTM