SystemUI: Refactor ongoing action progress chip

* No ExecutorService, no Handler-based repeaters.
* Coroutines handle debounce, media ticker, stale checks, and delayed collapses.
* State runs on Dispatchers.Main.immediate, so you can drop most locking.
* Icon loads run on a background dispatcher, then return to main for cache and UI updates.
* Duplicate icon fetches for the same package get suppressed via inFlightIconLoads.
* destroy() cancels all jobs and scope, so you avoid leaks and stray callbacks.
* Clean up biggest duplication in StateCallback entirely.
* Kill IconFetcher separate utility.

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>

Author: neobuddy89