feat(e2e): add support running behind proxy (#5348)

* docs: update maintaining

* chore(e2e): add maxFailures to playwright

* fix(ci): skip submodule in e2e job

We don't need the submodules for the e2e job. This will speed up the
checkout step.

* feat(ci): add test-e2e-proxy job

This adds a new job to CI to run our tests behind Caddy and simulate
code-server running against a reverse-proxy.

* refactor: make e2e work with reverse proxy

This refactors the e2e test in a couple ways:
- remove setting cookie in localStorage (instead we pass --auth none)
- refactor address() method to account for reverse proxy logic

* Update test/e2e/models/CodeServer.ts

* Update test/playwright.config.ts

* Update test/utils/constants.ts

Co-authored-by: Asher <ash@coder.com>

* Update test/utils/helpers.ts

Co-authored-by: Asher <ash@coder.com>

Co-authored-by: Asher <ash@coder.com>

test/playwright.config.ts

@@ -12,6 +12,8 @@ const config: PlaywrightTestConfig = {
   testDir: path.join(__dirname, "e2e"), // Search for tests in this directory.
   timeout: 60000, // Each test is given 60 seconds.
   retries: process.env.CI ? 2 : 1, // Retry in CI due to flakiness.
+  // Limit the number of failures on CI to save resources
+  maxFailures: process.env.CI ? 3 : undefined,
   globalSetup: require.resolve("./utils/globalE2eSetup.ts"),
   reporter: "list",
   // Put any shared options on the top level.