Admin Dashboard: Get KAS version from server and show a link

• Please check this box if this contribution uses AI-generated content (including content generated by GitLab Duo features) as outlined in the GitLab DCO & CLA

What does this MR do and why?

Part of #458891

Update the KAS version displayed on admin dashboard to:

1. Switch from the static GITLAB_KAS_VERSION to the GetServerInfo gRPC call

2. Adjust how the KAS version is displayed on UI according to !163830 (comment 2074925744):

   For the admin panel: We could concatenate the version and git_ref like so <version> (<git_ref), e.g. 17.4.0 (abcdef).

   See the before/after screenshots below.

MR acceptance checklist

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

Screenshots or screen recordings

	Before	After
KAS enabled		When KAS git_ref is a commit: When KAS git_ref is a tag (simulated via build_info.go): When getServerInfo RPC failed:
KAS not enabled (unchanged)	Not shown under "Components"	Not shown under "Components"

OPTIONAL: Use this table when providing screenshots at relevant viewport sizes. Delete table rows that are not relevant to your changes.

Viewport size	Before	After
xs (<576px)
sm (>=576px)
md (>=768px)
lg (>=992px)
xl (>=1200px)

How to set up and validate locally

1. Start GDK and visit /admin.
2. KAS is not enabled by default, so there should not be a GitLab KAS under Components.
3. Enable KAS in GDK (e.g. gdk config set gitlab_k8s_agent.enabled true && gdk reconfigure && gdk restart rails)
4. Check the GitLab KAS under `Components. The link should point to a KAS commit.
5. To test with different git_ref like a git tag, configure run_from_source, modify build_info.go, and gdk restart gitlab-k8s-agent. The getServerInfo RPC should return the value from build_info.go. e.g.

   gdk rails console
   [1] pry(main)> c = Gitlab::Kas::Client.new
   => #<Gitlab::Kas::Client:0x000000014d298738>
   [2] pry(main)> c.get_server_info
   => <Gitlab::Agent::ServerInfo::ServerInfo: version: "v0.0.0", git_ref: "0000000000000000000000000000000000000000">

6. To simulate a getServerInfo RPC call failure, run gdk stop gitlab-k8s-agent to bring down KAS.

Related to #458891