Part of MDL-79973. 

Background:
MDL-82916, MDL-82918 and MDL-84415 deal with the precursors to this issue: moving existing links to core_ltix, and adding a new API for CRUD of resource_links in core_ltix.

Goals:
Once those links are stored in core_ltix, the next focus is on updating the launch process + any relevant APIs, to make use these centrally located resource links. The idea is that consumer components (e.g. mod_lti) will store (or have existing stored, in the case of upgrading sites) resource links in core_ltix and then ask core_ltix to do a launch for a given resource link. The entire launch process for resource link should be controlled by core_ltix but easily consumable by other components, like mod_lti.

Other notes:

1. Need to migrate the relevant fields from mod_lti's 'lti' table to core_ltix as part of this work. E.g.:

 $sql = "INSERT INTO {lti_resource_link} (typeid, contextid, legacyid, url, title, text, textformat, launchcontainer, 

                                 customparams, icon, servicesalt)

                         SELECT lti.typeid, ctx.id, lti.id, lti.toolurl, lti.name, lti.intro, lti.introformat, 

                                lti.launchcontainer, lti.instructorcustomparameters, lti.icon, lti.servicesalt

                           FROM {lti} lti

                           JOIN {context} ctx ON (ctx.instanceid = lti.course)

                          WHERE ctx.contextlevel = :contextlevel";

            $DB->execute($sql, ['contextlevel' => CONTEXT_COURSE]);            $ltirs = $DB->get_recordset('lti', null, '', 'id');

            foreach ($ltirs as $ltirecord) {

                $DB->set_field('lti_resource_link', 'uuid', \core\uuid::generate(), ['legacyid' => $ltirecord->id]);

            }

            $ltirs->close();

# This task deals only with launch: a separate task will deal with adding deep linking workflows. 

1. Must consider embed vs new window launches as part of the API