[Test] KT-61360: add tests for the IrFakeOverrideBuilder

Add tests for fake overrides with focus on java interoperability

Co-authored-by: Aleksandra Arsenteva <aleksandra.arsenteva@jetbrains.com>

compiler/testData/ir/irText/fakeOverrides/methodmodifiers/basicKotlinModifiersOverride.kt

@@ -0,0 +1,35 @@
+// TARGET_BACKEND: JVM
+// SEPARATE_SIGNATURE_DUMP_FOR_K2
+// ^ Difference in external
+
+// FILE: Java1.java
+
+public class Java1 extends A { }
+
+// FILE: 1.kt
+
+open class A {
+    inline fun foo() {}
+    open external fun foo2()
+    open suspend fun foo3() {}
+    inline fun <reified T> foo4(t: T){}
+}
+
+class B : Java1()   //Kotlin ← Java ← Kotlin
+
+class C : Java1() { //Kotlin ← Java ← Kotlin with explicit override
+    override suspend fun foo3() { }
+    override fun foo2() {}
+}
+
+suspend fun test(b: B, c: C) {
+    b.foo()
+    b.foo2()
+    b.foo3()
+    b.foo4(1)
+
+    c.foo()
+    c.foo2()
+    c.foo3()
+    c.foo4("")
+}