(cherry picked from commit d6dbcab from Rider fork)

So users won't need to commit one more file into VCS (IDEA-CR-27985).

Expected class versions updated (IDEA-CR-27988).

because it is more like a collision in names (which was OK before we decided to unbound UElements from PsiElements) than a wrong usage.

To restore compatibility with Java 6. However since gradle-tooling-extension-impl module uses org.gradle.plugins.ide.idea.IdeaPlugin class which has version 51 (Java 7) in gradle API 4.4 we cannot use 'IDEA jdk' (JDK 6) in that module so we use the default project JDK (JDK 8) and add a compatibility check to ensure that classes from such modules won't use API which aren't available in JDK 1.6.

redundant throws inspection: mark all problems in method hierarchy as fixed when has been applied to super method

This is needed to be able to convert Guava to a repository library.

Using the same name and family name is ok in this case as name does not add any specific information.
Fixes EA-114106.

IDEA-183585 Mismatching @NotNull/@Nullable values for several method with identical signatures in inherited classes are not detected