[feature/twig] INCLUDEJS behavior now supports local relative paths

This was done because T_TEMPLATE_PATH is not always correct for js files
(e.g. the inheriting style does not include these). Now we use the Twig
Loader to find the correct file to link to (most specific file first, then
parent styles). Also allows using @namespace convention

PHPBB3-11598
[feature/twig] INCLUDEPHP behavior now supports local relative paths

As a last resort, now we use the Twig Loader to find the correct file to
include to (most specific file first, then parent styles). Also allows
using @namespace convention. This is ONLY done if the specified path is not
an absolute path AND the file does not exist relative to the phpBB root path.

PHPBB3-11598
[feature/twig] Fix template test case

PHPBB3-11598
[feature/twig] Fix includejs test

PHPBB3-11598