Centralize credential handling

My thinking is that this may reduce the cognitive overhead for
developers writing new test suites.

This also allows us to perform different setup steps (like ensuring the
editor is visible when authenticated).

test/e2e/browser.test.ts

@@ -1,7 +1,7 @@
 import { describe, test, expect } from "./baseFixture"
 
 // This is a "gut-check" test to make sure playwright is working as expected
-describe("browser", () => {
+describe("browser", true, () => {
   test("browser should display correct userAgent", async ({ codeServerPage, browserName }) => {
     const displayNames = {
       chromium: "Chrome",