FIR2IR: Rework resulted overridden-relation structure

The difference is how we deal with intermediate fake overrides
E.g., in case

interface A { /* $1 */ fun foo() }
interface B : A {
     /* $2 */ fake_override fun foo()
}
interface C : B {
   /* $3 */ override fun foo()
}

We've got FIR declarations only for $1 and $3, but we've got
a fake override for $2 in IR.

Previously, override $3 had $1 as its overridden IR symbol, just because
FIR declaration of $3 doesn't know anything about $2.

Now, when generating IR for $2, we save the necessary information
and using it for $3, so it has $2 as overridden.

So, it's consistent with the overridden structure of FE 1.0 and this
structure is necessary prerequisite for proper building of bridges
for special built-ins.

compiler/testData/codegen/box/collections/addCollectionStubWithCovariantOverride.kt

@@ -1,5 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
-
 abstract class AbstractAdd {
     abstract fun add(s: String): Any
 }
@@ -23,4 +21,4 @@ fun test2(a: AbstractStringCollection) =
     a.add("K") as String
 
 fun box() =
-    test1(StringCollection()) + test2(StringCollection())
+    test1(StringCollection()) + test2(StringCollection())

compiler/testData/codegen/box/collections/javaCollectionWithRemovePrimitiveInt.kt

@@ -1,5 +1,4 @@
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND_FIR: JVM_IR
 // WITH_RUNTIME
 // FILE: javaCollectionWithRemovePrimitiveInt.kt