inlineImages: Setting of image.crossOrigin is not always necessary (#1468)

Setting of the `crossorigin` attribute is not necessary for same-origin images, and causes an immediate image reload (albeit from cache) necessitating the use of a load event listener which subsequently mutates the snapshot.  This change allows us to  avoid the mutation of the snapshot for the same-origin case.

* Modify inlineImages test to remove delay and show that we can inline images without mutation

* Add an explicit test for when the `image.crossOrigin = 'anonymous';` method is necessary.  Uses a combination of about:blank and our test server to simulate a cross-origin context

* Other test changes: there were some spurious rrweb mutations being generated by the addition of the crossorigin attribute that are now elimnated from the rrweb/__snapshots__/integration.test.ts.snap after this PR - this is good

packages/rrweb-snapshot/test/utils.ts

@@ -1,4 +1,5 @@
 import * as puppeteer from 'puppeteer';
+import * as http from 'http';
 
 export async function waitForRAF(page: puppeteer.Page) {
   return await page.evaluate(() => {
@@ -9,3 +10,12 @@ export async function waitForRAF(page: puppeteer.Page) {
     });
   });
 }
+
+export function getServerURL(server: http.Server): string {
+  const address = server.address();
+  if (address && typeof address !== 'string') {
+    return `http://localhost:${address.port}`;
+  } else {
+    return `${address}`;
+  }
+}