This is basically a copy of the test
`diagnostics/tests/j+k/primitiveOverrides/triangleWithFlexibleTypeAndSubstitution4.kt`.
The diagnostic version of the test is not removed because it has
frontend-specific diagnostics `FIR_DUMP` and `SCOPE_DUMP`.
This test is copied to make it clear that it actually passes in K1, and
new errors in K2 here are technically a breaking change, see KT-66529.
The error CONFLICTING_INHERITED_JVM_DECLARATIONS was present there only
because diagnostic tests used parts of the old JVM backend to report JVM
backend diagnostics.
#KT-66529
Alexander Udalov
d08c904b0c