CI: Don't navigate to builds page when retry/canceling a build

Would be nice to be able to cancel a lot of builds (not all, selectively!) without having to click this cancel button, navigate back and wait every time. (Batch operations for issues would also be nice btw. Ever thought about that?)

EDIT:

We need a way to tell the user if the action was succeeded in order to give feedback regarding the action instead of redirecting the user to other page.

This currently happens in:

Where	Status
Pipelines page, in the mini pipelines graph, in the builds dropdown	Currently this receives HTML, we need to move into JSON first
Commits page, under the Pipelines tab, in the mini pipelines graph, in the builds dropdown	Same as above
Merge Request page, under the Pipelines tab, in the mini pipelines graph, in the builds dropdown	This is HAML
Big pipeline graph for each stage	This is Vue, we can start
Big pipeline graph, in the builds dropdown	This is Vue, we can start
Builds list in the builds page	This is haml
Commits page, under the Builds tab, in the table	This is haml
Merge Request page, under the Builds tab, in the table	This is haml
Pipeline show page - header buttons	Done in !11797 (merged)