Resolve "repository name bug"

What does this MR do and why?

• fixes the collapse of the breadcrumb - it only collapses when there is not enough space and uncollapses where there's more space
• uses GlBreadcrumb built-in copy-to-clipboard button
• uses GlBreadcrumb in the correct CSS flexbox context, which gets rid of the flickering collapse button

References

• repository name bug (#571470 - closed)
• [BUG] File breadcrumbs unnecessarily and random... (#570241)
• Add a slot to GlBreadcrumbs last item to popula... (gitlab-org/gitlab-services/design.gitlab.com#2918 - closed)
• Follow-up from "fix(GlBreadcrumb): Include clip... (gitlab-org/gitlab-services/design.gitlab.com#3170)

Screenshots or screen recordings

Before	After
Screen_Recording_2025-11-12_at_16.09.39	Screen_Recording_2025-11-12_at_16.07.15

How to set up and validate locally

Warning

Make sure you GDK is running with https enabled! Otherwise navigator.clipboard is undefined and clipboard button will throw an error!

1. Go to a project
2. Navigate inside a folder, make sure you have a couple of items in your repository breadcrumb. I recommend this GDK project: http://gdk.test:8080/gitlab-org/iglu/-/tree/master/src/test/java/com/example/demo
3. Adjust the width of the browser's window. Make sure the breadcrumbs collapse, when there's not enough space and expand when you go back to a wide window. The first item shouldn't flicker, when the breadcrumbs are in a collapsed state.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #571470 (closed) #570241