[FE] Cover "implicit actualization"/"actual fake-overrides" KT-58544 with regression tests

Review: https://jetbrains.team/p/kt/reviews/11039/timeline

compiler/testData/diagnostics/tests/multiplatform/actualFakeOverride.kt

@@ -0,0 +1,20 @@
+// FIR_IDENTICAL
+// MODULE: m1-common
+// FILE: common.kt
+
+expect class HashMap {
+    val size: Int
+}
+
+expect abstract class AbstractMap {
+    val size: Int
+}
+
+// MODULE: m2-jvm()()(m1-common)
+// FILE: jvm.kt
+
+actual abstract class AbstractMap() {
+    actual val size: Int = 0
+}
+
+actual class HashMap : AbstractMap()

compiler/testData/diagnostics/tests/multiplatform/actualFakeOverrideVirtual.kt

@@ -0,0 +1,24 @@
+// FIR_IDENTICAL
+// MODULE: m1-common
+// FILE: common.kt
+
+interface Map {
+    val size: Int
+}
+
+expect class HashMap : Map {
+    override val size: Int
+}
+
+expect abstract class AbstractMap : Map {
+    override val size: Int
+}
+
+// MODULE: m2-jvm()()(m1-common)
+// FILE: jvm.kt
+
+actual abstract class AbstractMap() : Map {
+    actual override val size: Int = 0
+}
+
+actual class HashMap : AbstractMap(), Map

compiler/testData/diagnostics/tests/multiplatform/implicitActualFakeOverride_AbstractMap.fir.kt

@@ -0,0 +1,15 @@
+// WITH_STDLIB
+// MODULE: m1-common
+// FILE: common.kt
+
+// K2: false positve INCOMPATIBLE_MATCHING: KT-60155
+<!INCOMPATIBLE_MATCHING{JVM}!>public expect abstract class AbstractMutableMap<K, V> : MutableMap<K, V> {
+    override val values: MutableCollection<V>
+}<!>
+
+// MODULE: m2-jvm()()(m1-common)
+// FILE: jvm.kt
+
+import java.util.AbstractMap
+
+public actual abstract class AbstractMutableMap<K, V>() : MutableMap<K, V>, AbstractMap<K, V>()

compiler/testData/diagnostics/tests/multiplatform/implicitActualFakeOverride_AbstractMap.kt

@@ -0,0 +1,15 @@
+// WITH_STDLIB
+// MODULE: m1-common
+// FILE: common.kt
+
+// K2: false positve INCOMPATIBLE_MATCHING: KT-60155
+public expect abstract class AbstractMutableMap<K, V> : MutableMap<K, V> {
+    override val values: MutableCollection<V>
+}
+
+// MODULE: m2-jvm()()(m1-common)
+// FILE: jvm.kt
+
+import java.util.AbstractMap
+
+public actual abstract class AbstractMutableMap<K, V>() : MutableMap<K, V>, AbstractMap<K, V>()

compiler/testData/diagnostics/tests/multiplatform/implicitActualFakeOverride_simple.kt

@@ -0,0 +1,16 @@
+// FIR_IDENTICAL
+// MODULE: m1-common
+// FILE: common.kt
+
+expect class Foo {
+    fun foo(): Int
+}
+
+// MODULE: m2-jvm()()(m1-common)
+// FILE: jvm.kt
+
+interface FooProvider {
+    fun foo(): Int = 42
+}
+
+actual class Foo : FooProvider