Fix path.scope.rename() to not change break clauses (#8478)

* Make labels on break and continue statements not referenced

* Add test for imports and labels with the same name

packages/babel-generator/test/fixtures/harmony-edgecase/import-with-break/input.js

@@ -0,0 +1,5 @@
+import foo from "foo";
+
+foo: {
+  break foo;
+}

packages/babel-generator/test/fixtures/harmony-edgecase/import-with-break/output.js

@@ -0,0 +1,5 @@
+import foo from "foo";
+
+foo: {
+  break foo;
+}

packages/babel-traverse/test/fixtures/rename/break-statements/input.js

@@ -0,0 +1,9 @@
+function f(a) {
+  a: for (const k in []) {
+    if (k) {
+      continue a;
+    } else {
+      break a;
+    }
+  }
+}

packages/babel-traverse/test/fixtures/rename/break-statements/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["./plugin"]
+}

packages/babel-traverse/test/fixtures/rename/break-statements/output.js

@@ -0,0 +1,9 @@
+function f(b) {
+  a: for (const k in []) {
+    if (k) {
+      continue a;
+    } else {
+      break a;
+    }
+  }
+}

packages/babel-traverse/test/fixtures/rename/break-statements/plugin.js

@@ -0,0 +1,9 @@
+module.exports = function() {
+  return {
+    visitor: {
+      Function(path) {
+        path.scope.rename("a", "b");
+      }
+    }
+  };
+}

packages/babel-types/src/validators/isReferenced.js

@@ -80,6 +80,10 @@ export default function isReferenced(node: Object, parent: Object): boolean {
     case "RestElement":
       return false;
 
+    case "BreakStatement":
+    case "ContinueStatement":
+      return false;
+
     // no: function NODE() {}
     // no: function foo(NODE) {}
     case "FunctionDeclaration":