Feature: Add the ability to hide off-cpu samples (idle event loop, sleep, waiting on a lock, blocking on sync IPC)

At the moment the call tree always shows all samples, and we do not know which samples were collected in on-cpu thread states vs off-cpu thread states. An "off-cpu thread state" is when a thread is blocked or waiting on something, such as in the event loop or on a lock.

It would be great if we could have a mode where we only show "on-cpu" samples in the call tree. This would automatically eliminate the idle event loop time from the call tree. If we make that mode the default, it would address a common source of confusion for new users, and it would make the Firefox profiler behave more like other profilers.

We could have a checkbox like this: `[x] Include off-CPU samples`

In the profile format, we'd need a flag on each sample to indicate on-cpu vs off-cpu samples.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-617)