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/if.kt

@@ -0,0 +1,11 @@
+// HIGHLIGHT: INFORMATION
+
+fun abs(x: Int): Int {
+    // No highlighting here
+    <caret>return if (x > 0) {
+        x
+    }
+    else {
+        -x
+    }
+}