Remove some yield calls from staged ledger application

[georgeee]

Remove some yield calls from staged ledger diff application code, as these are no longer necessary after recent optimizations.

Subsequently simplify some code to live entirely in Result monad (and not in Deferred.Result).

TODO created as draft because currently staged ledger application still takes 1-3s for max-cost blocks. At the same time cutoff for long async job is 500 ms. Although for blocks for the current mainnet (given the zkapp softcap) it's likely less than 500 ms, it's still better to keep it here.

It could be cherry-picked to other branches if it eases debugging (e.g. sstack traces become way more infomative.

Checklist:

• Dependency versions are unchanged
  • Notify Velocity team if dependencies must change in CI
• Modified the current draft of release notes with details on what is completed or incomplete within this project
• Document code purpose, how to use it
  • Mention expected invariants, implicit constraints
• Tests were added for the new behavior
  • Document test purpose, significance of failures
  • Test names should reflect their purpose
• All tests pass (CI will check this if you didn't)
• Serialized types are in stable-versioned modules
• Does this close issues? None