Build/Test Tools: Pass GitHub Actions environment variables to the Docker container.

This ensures that `WP_UnitTestCase::skipOnAutomatedBranches()` has access to the `GITHUB_REF` and `GITHUB_EVENT_NAME` variables, so that some tests can be skipped when appropriate.

Additionally, account for renaming the `master` branch to `trunk` in November 2021.

Follow-up to [40241], [46999], [49264], [49267], [51868].

Fixes #55668.

git-svn-id: https://develop.svn.wordpress.org/trunk@53349 602fd350-edb4-49c9-b593-d223f7449a82

docker-compose.yml

@@ -41,6 +41,8 @@ services:
       - LOCAL_PHP_MEMCACHED=${LOCAL_PHP_MEMCACHED-false}
       - PHP_FPM_UID=${PHP_FPM_UID-1000}
       - PHP_FPM_GID=${PHP_FPM_GID-1000}
+      - GITHUB_REF=${GITHUB_REF-false}
+      - GITHUB_EVENT_NAME=${GITHUB_EVENT_NAME-false}
 
     volumes:
       - ./tools/local-env/php-config.ini:/usr/local/etc/php/conf.d/php-config.ini