2823fff63d
It was already reported in the K2+PSI mode, but not LT because BuilderFactoryForDuplicateClassNameDiagnostics relied on PSI, and did not do anything if PSI was missing. No tests were added because it fixes the already existing test `compiler/testData/cli/jvm/fileClassClashMultipleFiles` after the project is migrated to 2.0. #KT-59586