Move acceptance tests that crash the PHP built-in server to Apache

The PHP built-in server can crash when certain actions are performed in
Nextcloud (but although the crash is triggered by Nextcloud it does not
seem to be a Nextcloud bug), which can lead to failures in the
acceptance tests that would have otherwise passed.

A crash of the PHP built-in server during an acceptance test can be
identified by the message "sh: 1: kill: No such process" in the
acceptance tests output; as the PHP built-in server crashed its process
does no longer exist when it is tried to be killed when the scenario
ends.

Although the crash has been observed in other tests too it is more
prevalent in the tests for tags and the theming app. In order to
reduce the false positives those tests are now run on Apache instead of
on the PHP built-in sever. However, the rest of tests are still run on
the PHP built-in server due to its lower resource consumption.

In order to run a feature or just a scenario using Apache it has to be
tagged with "@apache"; features or scenarios without that tag (the
default) will run on the PHP built-in server instead.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>