java: add smart enter for incomplete ternary operator, DRY (IDEA-70189)

GitOrigin-RevId: 0f8fa9c23efc9cf2d3be079a7e80e7cbbcdfdce9

java/java-tests/testData/codeInsight/completeStatement/AddTernaryColon.java

@@ -0,0 +1,5 @@
+class Test {
+    Object f(Object result) {
+        return x == null ? null<caret>
+    }
+}

java/java-tests/testData/codeInsight/completeStatement/AddTernaryColon_after.java

@@ -0,0 +1,5 @@
+class Test {
+    Object f(Object result) {
+        return x == null ? null : <caret>
+    }
+}