Add test for extension properties declaration in IR

compiler/testData/ir/irText/declarations/extensionProperties.kt

@@ -0,0 +1,13 @@
+val String.test1 get() = 42
+
+var String.test2
+    get() = 42
+    set(value) {}
+
+class Host {
+    val String.test3 get() = 42
+
+    var String.test4
+        get() = 42
+        set(value) {}
+}