Make it clearer when the result set gets filtered

[simonswine]

By clicking into the Flame graph we currently allow a user to focus on a particular subset of the flame graph.

After having filtered it quite hard to tell for a user that they are no longer seeing the full trace.

Full flamegraph:

Subset of a flamegraph after clicking on runtime.gcBgMarkWorker:

I think it would be good to make the existence of a filter clearer, by displaying e.g. the breadcrumb to the clicked node:

Without any filter present:

/

When a node has been clicked:

/runtime.gcBgMarkWorker