Add loading indicator when fetching branches and prebuilds

[gtsiolis]

Problem to solve

Loading Branches and Prebuilds for a project can still take a while for active projects, see #5038.

Proposal

Until there's a better way to resolve these perfomance issues, we could introduce a loading indicator when fetching branches and prebuilds to improve the user experience.

This could use the loading indicator being introduced in #5236, see relevant diff. ⚫

Branches	Prebuilds

[atduarte]

It would be also good to do something similar in the prebuild page, as it starts with an "unknown prebuild" title

[gtsiolis]

@jankeromnes since you added the loading indicator on the Branches page in #5809, do you think it makes sense to do the same for the Prebuilds page as it could be slightly slow to fetch prebuilds for active projects. For example, see https://gitpod.io/t/gitpod/gitpod/prebuilds. ❓ Cc @AlexTugarev

[gtsiolis]

Looping in @jldec for visibility.

[jankeromnes]

Yes 👍 happy to add these.

[JanKoehnlein]

/schedule

[roboquat]

@JanKoehnlein: Issue scheduled in the meta team (WIP: 0)

In response to this:

/schedule

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[jankeromnes]

/schedule

Woohoo! Rock'n'roll 😎