for "Type may be weakened" inspection

Since IntelliJ project may contain circular dependencies with runtime scope only this shouldn't cause problems. This is needed to publish intellij.platform.ide.impl, intellij.platform.testFramework (IDEA-194148) and other modules.

It didn't work anyway.

ID is identity hashcode.
Given two DfaType-s from two branches of, for example, instanceof expression, there were two InstanceofInstruction-s,
which created two Mixin instances with different IDs, and then they were never merged.

intellij-community project configuration: set minimum required IDE version for IDEA project to 2018.3

Following similar change (9ff9493af5b) in idea-ultimate project.

Gradle: dispose existing wizard if any in tests before new wizard creation (IDEA-204753,IDEA-205334)