0.30.0

• [Major] Further improvements in exception handling — no failure exception is lost.
  • async and async-like builders cancel parent on failure (it affects CompletableDeferred, and all reactive integration builders).
  • This makes parallel decomposition exception-safe and reliable without having to rember about awaitAll (see #552).
  • Job() wih parent now also cancels parent on failure consistently with other scopes.
  • All coroutine builders and Job implementations propagate failure to the parent unless it is a CancellationException.
  • Note, "scoping" builders don't "cancel the parent" verbatim, but rethrow the corresponding exception to the caller for handling.
  • SupervisorJob() and supervisorScope { ... } are introduced, allowing for a flexible implementation of custom exception-handling policies, see a new section in the guide on supervision.
  • Got rid of awaitAll in documentation and rewrote currentScope section (see #624).
• [Major] Coroutine scheduler is used for Dispatchers.Default by default instead of deprecated CommonPool.
  • "DefaultDispatcher" is used as a public name of the default impl (you'll see it thread names and in the guide).
  • -Dkotlinx.coroutines.scheduler=off can be used to switch back to CommonPool for a time being (until deprecated CommonPool is removed).
• Make CoroutineStart.ATOMIC experimental as it covers important use-case with resource cleanup in finally block (see #627).
• Restored binary compatibility of Executor.asCoroutineDispatcher (see #629).
• Fixed OOM in thread-pool dispatchers (see #571).
• Check for cancellation when starting coroutine with Dispatchers.Unconfined (see #621).
• A bunch of various performance optimizations and docs fixes, including contributions from @AlexanderPrendota, @PaulWoitaschek.