Prepare for PHPUnit 10

Issue information

From user: fjgarlin

Related to !206 (merged) !205 (closed) !198 (merged)

Contribution record

Fork management

Problem/Motivation

Drupal 11 will likely ship with PHPUnit 10, and new arguments will need to be passed when running the "vendor/bin/phpunit" binary (concurrency off). The "run-tests.sh" (concurrency on) already takes care of this.

It seems like we'll need to add --process-isolation and --fail-on-deprecation options as it might otherwise fail.

Proposed resolution

See if we can add the options now without PHPUnit 9 erroring, otherwise detect PHPUnit version and adapt parameters accordingly.