Use @web/test-runner which is toolset by the modern-web.dev and
open-wc.org initiatives. It is based on mocha and es-dev-server,
which allows to run our JavaScript modules natively in the browser
(without having to bundle them via rollup).

Note that compiled test files have been removed from the
source tree, since we configure es-dev-server to transpile
them on demand, allowing error output from tests to be
using original line numbers and unmangled identifiers.

The tests are executed in chrome by default (locally and CI).
They can be executed via:

  # Run once
  npm run test

  # Run tests whenever files change
  npm run watch:build
  npm run watch:test

  # Open browser with devtools and debug mode activated
  MODE=dev npm run watch:test -- --debug

Configuration is prepared to run in multiple browsers via playwright.
Example:

  # https://playwright.dev/docs/browsers#install-system-dependencies
  npx playwright install --with-deps
  BROWSERS=chrome,chromium,firefox,webkit npm run test

Commands executed:

  npm remove \
    karma \
    karma-chrome-launcher \
    karma-coverage \
    karma-jasmine \
    karma-junit-reporter \
    karma-rollup-preprocessor \
    jasmine-core \
    @types/jasmine

  npm install --save-dev \
    @web/test-runner \
    @web/test-runner-playwright \
    @web/dev-server-import-maps \
    @web/dev-server-esbuild \
    @open-wc/testing \
    sinon

  git rm -rf \
    typo3/sysext/core/Tests/JavaScript \
    typo3/sysext/backend/Tests/JavaScript

  npm run build

Resolves: #101960
Releases: main, 12.4
Change-Id: Ia2fa94a9f6d66664d9fce72e7443aaeb12e0ca08
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81096


Tested-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>