Add helpers to init GlToggle instances

What does this MR do and why?

This adds HAML and Js helpers to easily instantiate GlToggle from a HAML view.

Screenshots or screen recordings

The following previews are from other branches that leverage those helpers to replace existing toggle implementations.

Protect a branch (!80548 (merged))

Before	After

Edit protected branches (!80549 (merged))

Before	After

Toggling protected branches' status (!80549 (merged))

Screen_Recording_2022-02-10_at_11.47.42_AM

How to set up and validate locally

1. Pull any of the follow-up MRs.
2. In any project, navigate to the protected branch settings at /:namespace/:project/-/settings/repository#js-protected-branches-settings.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #344104 (closed)