[FIR] Only add non-subsumed to overridden of intersection override

If an intersection override overrides members A.x, B.x and C.x and
B <: A, then A.x is subsumed by B.x, and we don't add it to the list of
overridden members. This fixes a false-positive MANY_IMPL_MEMBER_NOT_
IMPLEMENTED where an implementation is subsumed by an abstract override.

^KT-57092 Fixed

compiler/fir/tree/src/org/jetbrains/kotlin/fir/ClassMembers.kt

@@ -111,6 +111,8 @@ inline fun <reified D : FirCallableDeclaration> D.unwrapSubstitutionOverrides():
 
 inline fun <reified S : FirCallableSymbol<*>> S.unwrapFakeOverrides(): S = fir.unwrapFakeOverrides().symbol as S
 
+inline fun <reified S : FirCallableSymbol<*>> S.unwrapSubstitutionOverrides(): S = fir.unwrapSubstitutionOverrides().symbol as S
+
 private object SubstitutedOverrideOriginalKey : FirDeclarationDataKey()
 
 var <D : FirCallableDeclaration>