[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/codegen/box/collections/kt48945b.jvm_abi.txt

@@ -0,0 +1,10 @@
+MODULE main
+	CLASS Test.class
+		K1
+			getOrDefault(Ljava/lang/Object;Ljava/lang/String;)Ljava/lang/String; [public, final, bridge]
+		K2
+			---
+		K1
+			getOrDefault(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String; [public, bridge]
+		K2
+			---