Right now we have one core function:
that returns all the plugins supported by moodle. It's used in upgrade code to look for upgrades under all plugins.
In the other side, we have the function:
that returns all the directories where we can found database install/upgrade scripts (used by the xmldb editor, database manager...)
And right now, both functions are 100% separate, having to keep such lists maintained manually.
Solution: Let's modify get_db_directories() in order to use get_plugin_types() to know about all the dirs being candidates to have install/upgrade/xmldb editor... scripts recognising the same plugins always.