[FIR] Don't remove subsumed members from intersection overrides's overriddens

This fixes a bunch of missing overridden symbols in IR.
This is also required for fixing KT-59921 in the following commit
where we need to keep all overridden symbols of intersection overrides
so that we can enhance them properly.

#KT-57300 Fixed
#KT-57299 Fixed
#KT-59921
#KT-57300
#KT-62788
#KT-64271
#KT-64382

compiler/testData/diagnostics/tests/j+k/orderOfSupertypesAndFakeOverrides_1.fir.kt

@@ -12,7 +12,7 @@ abstract class Derived : Base {
 class InterfaceThenClass : Base, Derived() {}
 
 fun test_1(x: InterfaceThenClass, s: String?) {
-    x.delete(<!ARGUMENT_TYPE_MISMATCH!>s<!>)
+    x.delete(s)
 }
 
 class ClassThenInterface : Derived(), Base {}