Memory leak with new memory model and withTimeout

[qwwdfsad]

See https://youtrack.jetbrains.com/issue/KTOR-4298 for details.

The root cause is our dispatcher implementation:

override fun invokeOnTimeout(timeMillis: Long, block: Runnable, context: CoroutineContext): DisposableHandle {
    // No API to cancel on timeout
    worker.executeAfter(timeMillis.toMicrosSafe()) { block.run() }
    return NonDisposableHandle
}

Yet it can be workarounded by carefully replacing lambda with something holding an atomic reference to a block so it can be nulled out

[alexvas]

@qwwdfsad, would you please publish 1.6.4-native-mt library version to Maven Central then?

[qwwdfsad]

The issues and the fix are related to regular versions of coroutine, the fix is not applicable for -native-mt versions