AbstractHighLevelMultiFileJvmBasicCompletionTest
Use `KotlinFixtureCompletionBaseTestCase` base because it can override `getProjectDescriptor`, so the tests will see full JDK Without it, there were problems when classes from JDK appeared in the completion (`Serialization`, for example)
Also remove `MultiFilePrimitiveJvmBasicCompletionTestGenerated` tests
#KT-11704 Fixed