[next] chore(NcBreadcrumbs): simplify code

[raimund-schluessler]

☑️ Resolves

This PR simplifies the code of NcBreadcrumbs.

• 825607a changes the render function to use a single Array.splice instead of slice -> push -> slice -> concat. This should speed up the render function a bit.
• 1ddda89 changes the breadcrumbsRefs object to be an array, which safes us from running Object.values at two spots.

I didn't send this PR against master to not introduce any issues in the stable branch. Also, merging changes to vue2 render functions into next is always a pain. In case you insist, we could of course also improve it for master.

No visual or functional changes.

Best viewed as https://github.com/nextcloud-libraries/nextcloud-vue/pull/5068/files?diff=unified&w=1

[susnux]

looks good to me

[raimund-schluessler]

Resolved conflicts.

[Antreesy]

Seems legit, code changes should be equivalent
Haven't work with array refs in Vue 3, but know they should work 🦭

[raimund-schluessler]

These random Cypress failures are annoying. Six runs now and always a different test failing.

[susnux]

These random Cypress failures are annoying. Six runs now and always a different test failing.

Yes that is super annoying, Cypress knows of that flaky tests for couple of month but is not considered to be something worth to fix.
@ShGKme mentioned PlayWright to me some time ago, since then I only use that for my personal projects, much less annoying 😅