Tests: Migrate test runner to jquery-test-runner

[timmywil]

Summary

I've moved all the code from test/runner into a package called jquery-test-runner. The changes to this repo are fairly simple. It uses the binary included in that package to run tests in browsers using selenium and browserstack.

Some things to note:

• I've tested jquery-test-runner with jquery, jquery-migrate, and jquery-ui and all their workflows have full green runs in my forks after migration.
• The jtr (alias for jquery-test-runner) binary includes several commands. The default command is for test runs (jtr or jtr run). jtr also includes jtr serve, which has a -p (--port) option (rather than an env var). See npx jtr --help for all commands and options.
• I've migrated yargs to commander in jquery-test-runner.
• I based the beginning infra of jquery-test-runner on the jquery repo's test/runner folder, which means the recent changes to allow Edge runs in IE-mode have been kept, express is not used for the test server, etc. jquery-migrate and jquery-ui will now be able to take advantage of those changes.
• jquery-test-runner can take a YAML config file, with support for all of the same options as the command line. I considered JSON and JS, but I liked how terse the YAML was. See jtr-isolate.yml for an example, which is used to create a separate run for each module in BrowserStack runs while still sharing browser instances.
• Upgraded the Node version used for testing to 22.x from 20.x in all workflows.

Ref jquery/jquery#5604

[mgol]

LGTM