Adding reusable new card styles

What does this MR do and why?

We introduced new card styles a while ago with slapping a bunch of gl- classes to elements. As we're continuing in slightly adjusting those styles and using it in more places it would be very helpful to have (gl-) classes available for faster adjustments and to ease maintenance.

The goal would be to update gl-card in the longtime but for the meantime we would include those updated styles directly in our product.

Structure:

.gl-new-card
  .gl-new-card-header
    .gl-new-card-title-wrapper
      .gl-new-card-title
    .gl-new-card-toggle
  .gl-new-card-body
    .gl-new-card-content
  .gl-new-card-footer

Screenshots or screen recordings

Before	After
Issue	Issue
Epic	Epic
Branches	Branches
Work items	Work items
Work items OKR	Work items OKR
Empty state	Empty state

How to set up and validate locally

1. Issue (e.g. http://gdk.test:3000/flightjs/Flight/-/issues/38)
2. Epic (e.g. http://gdk.test:3000/groups/flightjs/-/epics/5)
3. Branches (e.g. http://gdk.test:3000/flightjs/Flight/-/branches)

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.