Draft: Change titles to use type scale from GitLab UI

What does this MR do and why?

This MR's goal is to use the type scale for titles from the Pajamas Design System. Definition can be found here: GitLab UI Type definition
This change will also lead to greater uniformity of titles in our product once !88534 (merged) is merged.

Proposal

Make use of the type scale from GitLab UI.

@include gl-typescale-ui;

Screenshots or screen recordings

See it in action:

How to set up and validate locally

Go to an issue and check out the title on various breakpoints.

Related to #361641 (closed)