[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/testsWithStdLib/coroutines/mixingSuspendability.fir.kt

@@ -1,6 +0,0 @@
-interface AsyncVal { suspend fun getVal(): Int = 1}
-interface SyncVal { fun getVal(): Int = 1 }
-
-<!CONFLICTING_INHERITED_MEMBERS, MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class MixSuspend<!> : AsyncVal, SyncVal {
-
-}

compiler/testData/diagnostics/testsWithStdLib/coroutines/mixingSuspendability.kt

@@ -1,6 +1,7 @@
+// FIR_IDENTICAL
 interface AsyncVal { suspend fun getVal(): Int = 1}
 interface SyncVal { fun getVal(): Int = 1 }
 
-<!CONFLICTING_INHERITED_MEMBERS!>class MixSuspend<!> : AsyncVal, SyncVal {
+<!CONFLICTING_INHERITED_MEMBERS, MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class MixSuspend<!> : AsyncVal, SyncVal {
 
 }

compiler/testData/diagnostics/testsWithStdLib/coroutines/suspendOverridability.fir.kt

@@ -1,37 +0,0 @@
-// FILE: main.kt
-interface A {
-    suspend fun foo()
-    fun bar()
-}
-
-interface B : A {
-    override fun foo() {
-
-    }
-
-    override suspend fun bar() {
-
-    }
-}
-
-interface C : A {
-    suspend override fun foo() {
-
-    }
-
-    override fun bar() {
-
-    }
-}
-
-<!ABSTRACT_MEMBER_NOT_IMPLEMENTED!>class D<!> : J {
-    suspend override fun foo() {
-
-    }
-}
-
-// FILE: J.java
-
-public interface J extends A {
-    Object foo(kotlin.coroutines.Continuation<kotlin.Unit> y);
-}

compiler/testData/diagnostics/testsWithStdLib/coroutines/suspendOverridability.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: main.kt
 interface A {
     suspend fun foo()
@@ -5,11 +6,11 @@ interface A {
 }
 
 interface B : A {
-    <!CONFLICTING_OVERLOADS!><!NOTHING_TO_OVERRIDE!>override<!> fun foo()<!> {
+    override fun foo() {
 
     }
 
-    <!CONFLICTING_OVERLOADS!><!NOTHING_TO_OVERRIDE!>override<!> suspend fun bar()<!> {
+    override suspend fun bar() {
 
     }
 }