JetDiagnosticsTest migrated to TestGenerator

- test data files renamed from *.jet to *.kt

compiler/testData/diagnostics/tests/nullabilityAndAutoCasts/kt2125.kt

@@ -0,0 +1,12 @@
+//KT-2125 Inconsistent error message on UNSAFE_CALL
+
+package e
+
+fun main() {
+    val <!UNUSED_VARIABLE!>compareTo<!> = 1
+    val s: String? = null
+    s<!UNSAFE_CALL!>.<!>compareTo("")
+
+    val <!UNUSED_VARIABLE!>bar<!> = 2
+    s.<!UNRESOLVED_REFERENCE!>bar<!>()
+}