Replace work_lib hash table with ordered map

[georgeee]

Snark coordinator's Get_work RPC takes 400 ms to run on average.
With 20 workers, it puts a large burden onto snark coordinator.

This fix trims down Get_work RPC time to around 20 ms.

Explain your changes:

• Replace usage of hashtable with an ordered map

Explain how you tested your changes:

• Tested on a cluster with a snark coordinator and 20 workers with transaction generation set on
• Tested before and after the fix, snark coordinator's health improved substantially (it stopped being almost always out of sync)

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?

• Closes Snark coordinator falls into catchup/bootstrap too frequently #13453

[georgeee]

!ci-build-me

[georgeee]

!ci-build-me

[nholland94]

!approved-for-mainnet