Kotlin/kotlinx.coroutines 1.4.0 on GitHub

StateFlow, SharedFlow and corresponding operators are promoted to stable API (#2316).
Flow.debounce operator with timeout selector based on each individual element is added (#1216, thanks to @mkano9!).
CoroutineContext.job extension property is introduced (#2159).
Flow.combine operator is reworked:
- Complete fairness is maintained for single-threaded dispatchers.
- Its performance is improved, depending on the use-case, by at least 50% (#2296).
- Quadratic complexity depending on the number of upstream flows is eliminated (#2296).
- crossinline and inline-heavy internals are removed, fixing sporadic SIGSEGV on Mediatek Android devices (#1683, #1743).
Flow.zip operator performance is improved by 40%.
Various API has been promoted to stable or its deprecation level has been raised (#2316).

Suspendable stateIn operator propagates exception to the caller when upstream fails to produce initial value (#2329).
Fix SharedFlow with replay for subscribers working at different speed (#2325).
Do not fail debug agent installation when security manager does not provide access to system properties (#2311).
Cancelled lazy coroutines are properly cleaned up from debug agent output (#2294).
BlockHound false-positives are correctly filtered out (#2302, #2190, #2303).
Potential crash during a race between cancellation and upstream in Observable.asFlow is fixed (#2104, #2299, thanks to @LouisCAD and @drinkthestars).