JetDiagnosticsTest migrated to TestGenerator

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

compiler/testData/diagnostics/tests/nullabilityAndAutoCasts/kt2234.kt

@@ -0,0 +1,19 @@
+package a
+
+//KT-2234 'period!!' has type Int?
+
+fun main(args : Array<String>) {
+    val d : Long = 1
+    val period : Int? = null
+    if (period != null) #(d, period<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!> : Int) else #(d, 1)
+    if (period != null) #(d, period : Int) else #(d, 1)
+}
+
+fun foo() {
+    val x : Int? = 3
+    if (x != null)  {
+        val <!UNUSED_VARIABLE!>u<!> = x<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!> : Int
+        val y = x : Int
+        val <!UNUSED_VARIABLE!>z<!> : Int = y
+    }
+}