RUMM-1086 LongTaskObserver implemented

[buranmert]

What and why?

Long Tasks are events that occur when the main thread is blocked for more than the given threshold.
This event can show our users whether their apps block the main thread longer than needed and if so, how and when.

How?

RunLoopObservers added to RunLoop.main: they observe the intervals between run loop activites and report long intervals.
These observers act similarly to view and user action tracking.

TODO

• Add ObjC APIs

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference

[buranmert]

Tested in Example and works fine, but RunLoops seem to work differently in unit tests and my case doesn't pass. I'll keep it as draft until I figure this out.

[buranmert]

instead of fixing the problem in unit tests, we removed them in favor of integration tests ✅

[ncreated]

The actual code of observing long tasks (CFRunLoopObserver) looks fine 👍, but the way we collect LTs is missing few crucial elements which have no clear answers in proposed architecture:

• LTs are part of optional auto-instrumentation, configured with a public API (trackLongTasks() in Android SDK);
• LTs should not only be counted on view.longTask.count, but we should also send the LongTaskEvent (see: Android SDK);
• LTs should also be included in our data scrubbing API (through RUMEventMapper).

These all will come with its own configuration, lifecycle, threading and architectural problems, all solved in our existing auto-instrumentation stacks for actions and resources:

• RUMAutoInstrumentation → RUMCommand → RUMScope.

As long tasks collection is technically no different than collection of actions and resources, IMO it is better to just re-use existing concepts and architecture for implementing LTs. Otherwise, we'll have to find new solutions to these known problems, through VitalReader.

[ncreated]

🎯 💯 Looks great 👌. I left few small comments and one potential bug indication.

[ncreated]

🚀