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/overridePublicFun.kt.after

@@ -0,0 +1,7 @@
+open class A {
+    public open fun foo(): String = ""
+}
+
+class B : A() {
+    public override fun foo()<selection>: String</selection> = "abc"
+}