[FIR] Check conflicting overloads via scopes

Scopes may return private symbols from
supertypes, they should not clash with
symbols from the current class.

For example, see:
`FirLightTreeBlackBoxCodegenWithIrFakeOverrideGeneratorTestGenerated.FakeOverride#testPrivateFakeOverrides1`

Lombok shouldn't generate functions if the
user has defined explicit ones.

In K1 generated functions are not really
added to the declared members scope.

^KT-61243 Fixed

compiler/testData/diagnostics/tests/delegation/clashes/finalMemberOverridden.fir.kt

@@ -0,0 +1,55 @@
+open class Final {
+    fun foo() {}
+    val bar: Int = 0
+    var qux: Int = 0
+}
+
+open class Derived : Final()
+
+interface IFoo {
+    fun foo()
+}
+
+class CFoo : IFoo {
+    override fun foo() {}
+}
+
+interface IBar {
+    val bar: Int
+}
+
+class CBar : IBar {
+    override val bar: Int get() = 0
+}
+
+interface IQux {
+    val qux: Int
+}
+
+class CQux : IQux {
+    override val qux: Int get() = 0
+}
+
+interface IBarT<T> {
+    val bar: T
+}
+
+class CBarT<T> : IBarT<T> {
+    override val bar: T get() = null!!
+}
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class <!CONFLICTING_OVERLOADS, CONFLICTING_OVERLOADS!>Test1<!><!> : Final(), IFoo by CFoo()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class <!REDECLARATION, REDECLARATION!>Test2<!><!> : Final(), IBar by CBar()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION, VAR_OVERRIDDEN_BY_VAL_BY_DELEGATION!>class <!REDECLARATION, REDECLARATION!>Test3<!><!> : Final(), IQux by CQux()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class <!CONFLICTING_OVERLOADS, CONFLICTING_OVERLOADS!>Test4<!><!> : Derived(), IFoo by CFoo()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class <!REDECLARATION, REDECLARATION!>Test5<!><!> : Derived(), IBar by CBar()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION, VAR_OVERRIDDEN_BY_VAL_BY_DELEGATION!>class <!REDECLARATION, REDECLARATION!>Test6<!><!> : Derived(), IQux by CQux()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class <!REDECLARATION, REDECLARATION!>Test7<!><!> : Final(), IBarT<Int> by CBarT<Int>()
+
+<!OVERRIDING_FINAL_MEMBER_BY_DELEGATION!>class <!REDECLARATION, REDECLARATION!>Test8<!><!> : Final(), IBarT<Int> by <!TYPE_MISMATCH!>CBar()<!>

compiler/testData/diagnostics/tests/delegation/clashes/finalMemberOverridden.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 open class Final {
     fun foo() {}
     val bar: Int = 0