When recording specific threads, show those threads in the profile UI

When profiling media workloads, we add manually a bunch of threads in the textbox. When capturing the profile and displaying it in the UI, those threads are not shown automatically.

The intent of the user is quite clear: they want to look at what those threads were doing, so it would be best if they were shown in the profiler UI directly.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-189)