Move away from the karma test runner for browser tests

[timostamm]

We test web clients on browsers via browserstack with the jasmine test framework and karma, which has an integration with browserstack. (See here for details.)

Karma is deprecated since April 2023, and we should move to an alternative mechanism to ensure compatibility with old browser.

[timostamm]

We started using webdriverio for conformance tests. It appears to support browserstack, which means that we're potentially able to run the conformance tests against older web browsers. This would be desirable because it gives us better coverage, and removes the need for handwritten tests specific for browserstack.

[timostamm]

This ran successfully for me:

import {remote} from "webdriverio";

const browserstackUsername = process.env.BROWSERSTACK_USERNAME ?? "";
const browserstackAccessKey = process.env.BROWSERSTACK_ACCESS_KEY ?? "";
if (browserstackUsername.length == 0 || browserstackAccessKey.length == 0) {
  throw new Error(
    "The environment variables BROWSERSTACK_USERNAME and BROWSERSTACK_ACCESS_KEY are required to run tests on browserstack.",
  );
}

const browser = await remote({
  user: browserstackUsername,
  key: browserstackAccessKey,
  services: [
    ["browserstack", {
      // browserstackLocal: true
    }]
  ],
  capabilities: [
    {
      browserName: 'Chrome',
      'bstack:options': {
        browserVersion: '120.0',
        os: 'Windows',
        osVersion: '10'
      }
    },
  ],
  // Directory to store all test runner log files (including reporter logs and wdio logs).
  // If not set, all logs are streamed to stdout, which conflicts with the conformance runner I/O.
  // outputDir: new URL("logs", import.meta.url).pathname,
});

await browser.url("https://connectrpc.com");

await browser.deleteSession();

[timostamm]

We started using webdriverio for conformance tests. It appears to support browserstack, which means that we're potentially able to run the conformance tests against older web browsers. This would be desirable because it gives us better coverage, and removes the need for handwritten tests specific for browserstack.

Tracking this separately in #1238.