Report a warning when comparing incompatible enums

I've put `isIncompatibleEnums` to TypeIntersector because I placed
all of its usages after all of the TypeIntersector::isIntersectionEmpty ones

^KT-28225 Fixed

compiler/testData/diagnostics/tests/enum/compareTwoDifferentEnums.kt

@@ -11,6 +11,6 @@ public enum JavaEnumB {}
 enum class KotlinEnumA
 enum class KotlinEnumB
 
-fun jj(a: JavaEnumA, b: JavaEnumB) = a == b
-fun jk(a: JavaEnumA, b: KotlinEnumB) = a == b
-fun kk(a: KotlinEnumA, b: KotlinEnumB) = a == b
+fun jj(a: JavaEnumA, b: JavaEnumB) = <!INCOMPATIBLE_ENUM_COMPARISON!>a == b<!>
+fun jk(a: JavaEnumA, b: KotlinEnumB) = <!INCOMPATIBLE_ENUM_COMPARISON!>a == b<!>
+fun kk(a: KotlinEnumA, b: KotlinEnumB) = <!INCOMPATIBLE_ENUM_COMPARISON!>a == b<!>