Always persist `processed` of CommitStatus

What does this MR do?

Since the same instance can go through multiple status transitions the subsequent changes to processed can be lost since the object is not refresh to exact DB state.

Always consider processed as a changed value and persist its current value.

Concurrency aspect explained: #220097 (comment 354004406).

Resolves the #220097 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content