Stop exposing the URL polyfill in the global scope

This moves/exposes the `URL` polyfill similarily to the existing `ReadableStream` polyfill, rather than exposing it globally, to avoid interfering with any "outside" code.
Both the `URL` and `ReadableStream` polyfills are now exposed on the `pdfjsLib` object, such that they are accessible to the viewer components.
Furthermore, the `no-restricted-globals` ESLint rule is also enabled to prevent accidental usage of the native `URL`/`ReadableStream` implementations directly in the `src/` and `web/` folders; see also https://eslint.org/docs/rules/no-restricted-globals

Addresses the remaining TODO in https://github.com/mozilla/pdf.js/projects/6

src/display/api.js

@@ -18,7 +18,7 @@ import {
   assert, createPromiseCapability, getVerbosityLevel, info, InvalidPDFException,
   isArrayBuffer, isSameOrigin, MissingPDFException, NativeImageDecoding,
   PasswordException, setVerbosityLevel, shadow, stringToBytes,
-  UnexpectedResponseException, UnknownErrorException, unreachable, warn
+  UnexpectedResponseException, UnknownErrorException, unreachable, URL, warn
 } from '../shared/util';
 import {
   DOMCanvasFactory, DOMCMapReaderFactory, DummyStatTimer, loadScript,