Implement intentions to add/remove braces to/from when entries #KT-12043 Fixed

idea/testData/intentions/addBracesToWhenEntry/.intention

@@ -0,0 +1 @@
+org.jetbrains.kotlin.idea.intentions.AddBracesToWhenEntryIntention

idea/testData/intentions/addBracesToWhenEntry/hasBraces.kt

@@ -0,0 +1,9 @@
+// IS_APPLICABLE: false
+
+fun foo(a: Int) {
+    when (a) {
+        1 -> {
+            foo(a)<caret>
+        }
+    }
+}

idea/testData/intentions/addBracesToWhenEntry/simple.kt

@@ -0,0 +1,5 @@
+fun foo(a: Int) {
+    when (a) {
+        1 -> foo(a)<caret>
+    }
+}

idea/testData/intentions/addBracesToWhenEntry/simple.kt.after

@@ -0,0 +1,7 @@
+fun foo(a: Int) {
+    when (a) {
+        1 -> {
+            foo(a)
+        }<caret>
+    }
+}