In this commit, tests where backend diagnostics were reported correctly
are being moved.
FirScopeDumpHandler was added to FIR diagnostic tests with JVM backend
to support `SCOPE_DUMP` in `overridesBuiltinNoMagic.kt` and
`charAtAndOverload.kt`.
In most affected tests, the backend diagnostic such as "conflicting JVM
signature" or "accidental override" is directly caused by some already
existing error reported by frontend, so it doesn't make sense to check
backend diagnostics there.
Tests where that was not the case were moved/copied to
`testsWithJvmBackend`.