Created module idea-test-framework and moved classes needed for idea tests there

Moved tests for completion and their test data into module idea-completion

idea/idea-completion/testData/basic/common/extensions/Extensions.kt

@@ -0,0 +1,21 @@
+package a.b
+
+class Some {
+    inner class Inner {
+        fun foo() {
+            "".<caret>
+        }
+
+        fun String.memberExtFun() { }
+    }
+
+    val String.memberExtProp: Int get() = 1
+}
+
+fun String.extFun() { }
+val String.extProp: Int get() = 1
+
+// EXIST: { lookupString: "extFun", itemText: "extFun", tailText: "() for String in a.b", typeText: "Unit" }
+// EXIST: { lookupString: "extProp", itemText: "extProp", tailText: " for String in a.b", typeText: "Int" }
+// EXIST: { lookupString: "memberExtFun", itemText: "memberExtFun", tailText: "() for String in Some.Inner", typeText: "Unit" }
+// EXIST: { lookupString: "memberExtProp", itemText: "memberExtProp", tailText: " for String in Some", typeText: "Int" }