Make "Specify explicit lambda signature" available on whole lambda

So #KT-22492 Fixed

idea/testData/intentions/specifyExplicitLambdaSignature/cursorOnRightBrace.kt

@@ -0,0 +1,4 @@
+fun foo(f: (String) -> Int) {}
+fun test() {
+    foo { it.length <caret>}
+}

idea/testData/intentions/specifyExplicitLambdaSignature/cursorOnRightBrace.kt.after

@@ -0,0 +1,4 @@
+fun foo(f: (String) -> Int) {}
+fun test() {
+    foo { it: String -> it.length <caret>}
+}

idea/testData/intentions/specifyExplicitLambdaSignature/invalidCursorPosition.kt

@@ -1,4 +0,0 @@
-// IS_APPLICABLE: false
-fun main() {
-    val sum : (Int, Int) -> Int = { x, y -> <caret>x + y }
-}