[FIR2IR] Always look for already generated fake overrides before creating them

This change covers the case where some f/o was generated in common module
  and it is referenced in platform code. But signature of this f/o may be
  different in different modules because of e.g. actualization of value
  parameters with actual typealias

^KT-60850 Fixed

compiler/testData/codegen/box/multiplatform/k2/basic/intersectionOverrideWithDefaultParameterInCommonModule.kt

@@ -0,0 +1,42 @@
+// LANGUAGE: +MultiPlatformProjects
+// IGNORE_BACKEND_K1: ANY
+// ISSUE: KT-60850
+// WITH_STDLIB
+
+// MODULE: common
+// FILE: common.kt
+
+expect class Expect {
+    fun foo(): String
+}
+
+interface Base {
+    fun cancel(s: Expect? = null): String
+}
+
+open class Derived : Base {
+    override fun cancel(s: Expect?): String {
+        return s?.foo() ?: "OK"
+    }
+}
+
+open class AbstractImpl : Derived(), Base
+
+// MODULE: platform()()(common)
+// FILE: platform.kt
+
+class ActualTarget {
+    fun foo(): String = "Fail"
+}
+
+actual typealias Expect = ActualTarget
+
+class Impl : AbstractImpl() {
+    fun test(): String {
+        return cancel()
+    }
+}
+
+fun box(): String {
+    return Impl().test()
+}

compiler/testData/codegen/box/multiplatform/k2/basic/localIntersectionOverrideWithDefaultParameterInCommonModule.kt

@@ -0,0 +1,55 @@
+// LANGUAGE: +MultiPlatformProjects
+// IGNORE_BACKEND_K1: ANY
+// ISSUE: KT-60850
+// WITH_STDLIB
+
+// MODULE: common
+// FILE: common.kt
+
+expect class Expect {
+    fun foo(): String
+}
+
+interface Base {
+    fun cancel(s: Expect? = null): String
+}
+
+open class Derived : Base {
+    override fun cancel(s: Expect?): String {
+        return s?.foo() ?: "OK"
+    }
+}
+
+open class AbstractImpl : Derived(), Base
+
+fun testCommon(): String {
+    class LocalCommon : AbstractImpl() {
+        fun test(): String {
+            return cancel()
+        }
+    }
+    return LocalCommon().test()
+}
+
+// MODULE: platform()()(common)
+// FILE: platform.kt
+
+class ActualTarget {
+    fun foo(): String = "Fail"
+}
+
+fun testPlatform(): String {
+    class LocalPlatform : AbstractImpl() {
+        fun test(): String {
+            return cancel()
+        }
+    }
+    return LocalPlatform().test()
+}
+
+actual typealias Expect = ActualTarget
+
+fun box(): String {
+    if (testCommon() != "OK") return "Fail"
+    return testPlatform()
+}