Finish removing requires of externallib.php from Report builder

This is to finish off the work started in MDL-76583 - in that issue, all external classes under the core_reportbuilder namespace were updated to use the new external APIs, but only 1/6 of the inplace editable output classes were updated:

https://github.com/moodle/moodle/commit/a3cc26f8bb8a9422a4b5a0ef3ff5f3551830d724#diff-7a45b2292ec2db39021b17d20808b909c840e2da9f80e547f28875abcf389dba

This issue will update the remaining 5, in turn removing the last remnants of /external/externallib.php from the Report builder component