Provide field type to allow for number type data to be stored and
presented within those components that already support custom fields.
This is especially useful for reporting purposes.
Remove functionality to migrate from MyISAM, and remove tests of whether
the existing database is using this.
Support for MyISAM was dropped in Moodle 2.9 (MDL-46064) so it should
not be possible for any subsequent Moodle version to be using this.
The only remaining MyISAM-aware code is the environment check via
check_database_storage_engine() to prevent installation/upgrade if the
database is set to use this.
Jun Pataleta