Put the auto-scroll toggle back into pipeline output view

Description

There used to be an auto-scroll button when viewing build output in a CI pipeline. That button was removed. It should not have been removed because, as a user, I want to be able to easily stop and restart auto-scroll.

Proposal

Put the original auto scroll button back in the product.

Links / references

https://gitlab.com/gitlab-org/gitlab-ce/issues/34846#note_39553787

Documentation blurb, Overview, Use cases, Feature checklist

(Same as for original auto-scroll button)

/cc @bikebilly @dimitrieh

added CI/CD UX feature proposal pipeline labels

mentioned in issue #37898