Expose RL modules and js config vars in action=expandtemplates

Expose RL modules and js config vars in action=expandtemplates

Adds the 'modules', 'jsconfigvars', and 'encodedjsconfigvars' props
to action=expandtemplates, that output the modules and Javascript
configuration variables added to ResourceLoader by extensions and
parser functions, in the same way action=parse does.

This is needed by Parsoid to correctly include all modules used by
parser functions.

Based on I5c3ccb25385e57633639bb0c7e6f562eb58b05a2 by @Jackmcbarn.

Bug: T69540
Change-Id: Iaf58c66c987a318c0dd1ee2b81774106c40e7561