[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/thisAndSuper/thisInPropertyInitializer.fir.kt

@@ -0,0 +1,8 @@
+interface Base {
+    fun foo()
+}
+val String.test: Base = object: Base {
+    override fun foo() {
+        this@test
+    }
+}