Most of these tests used this directive as a way to opt in to a new
language feature, and most of those features are already stable for a
long time, so no opt-in is needed. Some other tests used the directive
to opt out from a language feature, replace those by the `LANGUAGE`
directive. One test used the directive to test behavior that actually
depended on the API version; use `API_VERSION` directive there instead.
This patch mutes the following test categories:
* Tests with java dependencies (System class,
java stdlib, jvm-oriented annotations etc).
* Coroutines tests.
* Reflection tests.
* Tests with an inheritance from the standard
collections.
Change getAllOverriddenDescriptors contracti, now it returns
original (not substituted) descriptors without any duplicates.
First of all it's necessary in CodegenUtil.getDelegates to avoid
duplicates (see assertion there), but also it's convenient for all
other usages of this method
#KT-8154 Fixed
Mikhael Bogdanov