Create new pipelines from merge request

This is a duplicate of gitlab-foss#65940 (closed) which was implemented in %12.3

Description

On a recent update, our team has stopped the automatic creation of pipelines for branches other than master, instead opting to make it a manual process. However, to create a new pipeline for a merge request to ensure tests are passing before being passed on for review, you have to navigate away from the merge request:

CI / CD --> Pipelines --> Run Pipeline --> Select branch --> Create Pipeline

and then navigate back to the merge request.

Proposal

I propose a button within the merge request page, possibly within the 'Pipelines' tab, to shortcut this process.