The new resources in the "active tab" view should be reachable and actionable with the keyboard

As seen in the [current code](https://profiler.firefox.com/public/014dcadd045f9bc8d43359dbef1905a7a995d25f/calltree/?ctxId=12&resources&thread=19&v=4&view=active-tab) we can't reach or even expand the resources view with the keyboard. Once it's expand we can't expand a specific resource either.

The easiest is to use buttons. Either turn `timelineResourcesHeader` into a button or embed a button inside.
For individual resources probably make `timelineTrackResourceLabel` a button. I see that `mouseup` instead of `click` is handled here, so probably we would need to handle 'keydown', or use `click` instead of `mouseup` (I haven't looked at the code, only inspected with the devtools :) ).

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-273)