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/whenUnitWithElse.kt

@@ -0,0 +1,9 @@
+enum class AccessMode { READ, WRITE, RW }
+fun whenExpr(access: AccessMode) {
+    <caret>when (access) {
+        AccessMode.READ -> println("read")
+        AccessMode.WRITE -> println("write")
+        else -> println("else")
+    }
+}
+fun println(s: String) {}