[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/duplicateDefaultValuesSubsumedIntersection.kt

@@ -0,0 +1,13 @@
+// FIR_IDENTICAL
+
+interface SupervisorApiCallContextImpl : SupervisorApiCallDbContext, TxExecutor
+
+interface SupervisorApiCallDbContext : TxExecutor, DbContextOwner
+
+interface DbContextOwner : TxExecutor {
+    override fun foo(p: Int) {}
+}
+
+interface TxExecutor {
+    fun foo(p: Int = 1)
+}