Add regression tests for KT-46890 and other stuff

compiler/testData/codegen/box/inlineClasses/result/extensionOverride.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+fun <T> Result<T>.get(): T = getOrNull()!!
+
+interface C<T> {
+    abstract fun Result<T>.foo(): String
+}
+
+class D : C<String> {
+    override fun Result<String>.foo() = get()
+}
+
+fun <T> C<T>.bar(x: T) = Result.success(x).foo()
+
+fun box() = D().bar("OK")