Introduce "use expression body" inspection #KT-16063 Fixed

Converted from the relevant intention
Reported cases: one-liners, whens
Also, more exact caret detection in local inspection tests

idea/testData/inspectionsLocal/useExpressionBody/convertToExpressionBody/whenIfUnitNonExhaustive.kt

@@ -0,0 +1,11 @@
+// PROBLEM: none
+
+enum class AccessMode { READ, WRITE, RW }
+fun whenExpr(mode: Boolean, access: AccessMode) {
+    <caret>when (access) {
+        AccessMode.READ -> if (mode) println("read") else println("noread")
+        AccessMode.WRITE -> if (mode) println("write")
+        AccessMode.RW -> if (mode) println("both") else println("no both")
+    }
+}
+fun println(s: String) {}