The joubel/core and joubel/editor libraries have been moved to Moodle
namespace.
This commit adds the new namespace to the places where these classes
are used.
Besides, a couple of minor changes have been done to replace the _test.php
classname and remove some unnecessary defined('MOODLE_INTERNAL').

The joubel/editor is a third-party library. A namespace has been added to
avoid collision with other plugins using it (such as mod_hvp).
That way, they will be able to have a different version without
side effects.

The joubel/core is a third-party library. A namespace has been added to
avoid collision with other plugins using it (such as mod_hvp).
That way, they will be able to have a different version without
side effects.

* Plus use example domain for user email in the Behat test

When using a try/catch for a find if the first match is not met then we
have an implicit 6 second delay waiting for the search to time out.

We can avoid this by combining the searches in a comma-separated
selection.

I have also taken the opportunity to convert the use of ->click() to the
i_click_on function which has the benefit of supporting wait for
pendingJS.

The standard NodeElement functions for getAttribute, getTagName,
getParent, and friends go back to WebDriver and parse the DOM for each
request. This is insanely slow per request, and in the case of forms we
do a lot of checking to determine the field type.

This change modifies the form field detection to copy the entire node
content into a DOMDocument and parse the document locally.

This is significantly faster - in some cases where there are large
documents minutes faster.

I believe that this should be a safe change as the document fetched from
the browser is normalised to match the doctype specified.

The write_setting() should only use the internal validation if no validation function was provided