SCORU: rename sc-atomic-batch manager operation

Context

Addresses #3128 (closed). Rename the manager operation Sc_rollup_atomic_batch to Sc_rollup_execute_outbox_message to make it more generic.

We were also considering the wording "execute outbox effect" but to my mind it's less explicit. With "execute outbox message" it's clear that we're referring to a message existing in the rollup's outbox.

The types of messages may be extended in the future.

Manually testing the MR

CI.

Checklist

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