Job view dies if mem_bw metric not available

[fodinabor]

Related to #69 - for some reason mem_bw is not provided by the /{job-id}?metric=flops_any&metric=mem_bw&... request made when loading both, the job list as well as the job view.

When this happens, the whole page is stuck and does not allow clicking anything anymore.
The dev console prints the following error:

job.js:1 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'metric')
    at Array.J$ (job.js:1:334161)
    at u (job.js:1:536)
    at ko (job.js:1:55798)
    at We (job.js:1:10469)
    at new Oo (job.js:1:57102)
    at Array.Y$ (job.js:1:332872)
    at Object.p (job.js:1:335026)
    at p (job.js:1:894)
    at Object.p (job.js:1:132543)
    at ke (job.js:1:6235)

I guess [the roofline plot](https://github.com/ClusterCockpit/cc-backend/blob/e00e3208caefbba05cd19151a524b09cc0d41bce/web/frontend/src/Job.root.svelte#L118] just assumes that there's always a mem_bw metric (hardcoded :-() and thus has an invalid access there when it's not there.

[moebiusband73]

We also had issues with hanging views. And I also suspected that the access to the roofline metrics is hardcoded is the reason.
We will have a look at it.

[spacehamster87]

Moved .metric selection from Job-Root to Roofline-Component: Roofline now renders even if mem_bw and/or flops_any are missing.

Browser-Console logs more comprehensible errors. Analysis-View and Status-View unaffected by changes.