Set the SHA to be merged from push options

What does this MR do?

When we set merge_when_pipeline_succeeds in the push options, we also need to provide the sha that we'll be merging.

We take the cha from the changes list that was passed into the push options, and pass it onwards to the Create or Update service.

Closes #37061 (closed)

Does this MR meet the acceptance criteria?

Conformity

Availability and Testing

Edited by Bob Van Landuyt