Fix rest parameters indexing with TypeScript 'this parameter' (#9714)

* Fix rest parameters indexing with TypeScript 'this parameter'

The TypeScript [this parameter][0] is a fake parameter and should not be
taken into account when counting the function parameters.  This patch
skips it by using the condition taken from the `transform-typescript`
plugin.

Note: since the `transform-typescript` plugin is removing this kind of
parameter, including it before the `transform-parameters` plugin solves
the issue.  This patch fixes the issue in other cases.

[0]: https://www.typescriptlang.org/docs/handbook/functions.html#this-parameters

* nit: improve the 'this parameter' detection condition

* improve performance by checking the parameter list length before
accessing it
* simplify the test a bit by using the `isIdentifier` second
parameter

packages/babel-plugin-transform-parameters/test/fixtures/parameters/options.json

@@ -2,6 +2,7 @@
   "plugins": [
     "proposal-class-properties",
     "external-helpers",
+    "syntax-typescript",
     "syntax-flow",
     "transform-parameters",
     "transform-block-scoping",

packages/babel-plugin-transform-parameters/test/fixtures/parameters/rest-ts-this-parameter/input.js

@@ -0,0 +1,7 @@
+function u(this: Foo, ...items) {
+  items[0];
+}
+
+function v(this: Foo, event: string, ...args: any[]) {
+  args;
+}

packages/babel-plugin-transform-parameters/test/fixtures/parameters/rest-ts-this-parameter/output.js

@@ -0,0 +1,11 @@
+function u(this: Foo) {
+  arguments.length <= 0 ? undefined : arguments[0];
+}
+
+function v(this: Foo, event: string) {
+  for (var _len = arguments.length, args = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
+    args[_key - 1] = arguments[_key];
+  }
+
+  args;
+}