Run E2E tests with RoadRunner by default

[acelaya]

TODO:

• Make composer test:api run with RoadRunner, and replace test:api:rr with test:api:openswoole.
• Fix code coverage. Currently it is always reported as 0% with RoadRunner.
  • This is just not supported with RoadRunner: https://github.com/orgs/roadrunner-server/discussions/1440
• Adapt CI pipeline

[acelaya]

Blocked by RoadRunner not supporting code coverage generation via pcov or xdebug

• https://github.com/orgs/roadrunner-server/discussions/1440
• Coverage results in 0% when exported sebastianbergmann/php-code-coverage#1003

[acelaya]

In the end it turns out the missing coverage was not RoadRunner's fault. Instead, I had to move the .rr.yml config file used in tests to the project root, and everything started to work.