[e.cash] Change status of UTXO Commitments to Underway

Summary:
With the assumeutxo work, this feature is on its way.

Also add and "s" to Commitments, as this is the commonly used term.

Test Plan: Ran it locally and looked at the roadmap

Reviewers: PiRK, #bitcoin_abc

Reviewed By: PiRK, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D14997