Added tests for space insertion after return@xxx + do not overwrite space after keyword

idea/testData/completion/handlers/keywords/QualifiedReturnNonUnit.kt

@@ -0,0 +1,10 @@
+fun foo() {
+    takeHandler1 {
+        takeHandler2({ ret<caret> })
+    }
+}
+
+inline fun takeHandler1(handler: () -> Unit){}
+inline fun takeHandler2(handler: () -> String){}
+
+// ELEMENT: return@takeHandler2

idea/testData/completion/handlers/keywords/QualifiedReturnNonUnit.kt.after

@@ -0,0 +1,10 @@
+fun foo() {
+    takeHandler1 {
+        takeHandler2({ return@takeHandler2 <caret> })
+    }
+}
+
+inline fun takeHandler1(handler: () -> Unit){}
+inline fun takeHandler2(handler: () -> String){}
+
+// ELEMENT: return@takeHandler2

idea/testData/completion/handlers/keywords/QualifiedReturnNonUnitExplicit.kt

@@ -0,0 +1,10 @@
+fun foo() {
+    takeHandler1 {
+        takeHandler2({ (): String -> ret<caret> })
+    }
+}
+
+inline fun takeHandler1(handler: () -> Unit){}
+inline fun takeHandler2(handler: () -> String){}
+
+// ELEMENT: return@takeHandler2

idea/testData/completion/handlers/keywords/QualifiedReturnNonUnitExplicit.kt.after

@@ -0,0 +1,10 @@
+fun foo() {
+    takeHandler1 {
+        takeHandler2({ (): String -> return@takeHandler2 <caret> })
+    }
+}
+
+inline fun takeHandler1(handler: () -> Unit){}
+inline fun takeHandler2(handler: () -> String){}
+
+// ELEMENT: return@takeHandler2

idea/testData/completion/handlers/keywords/QualifiedReturnUnit.kt

@@ -0,0 +1,10 @@
+fun foo() {
+    takeHandler1 {
+        takeHandler2({ ret<caret> })
+    }
+}
+
+inline fun takeHandler1(handler: () -> Unit){}
+inline fun takeHandler2(handler: () -> String){}
+
+// ELEMENT: return@takeHandler1

idea/testData/completion/handlers/keywords/QualifiedReturnUnit.kt.after

@@ -0,0 +1,10 @@
+fun foo() {
+    takeHandler1 {
+        takeHandler2({ return@takeHandler1<caret> })
+    }
+}
+
+inline fun takeHandler1(handler: () -> Unit){}
+inline fun takeHandler2(handler: () -> String){}
+
+// ELEMENT: return@takeHandler1