Provide some way for an extension's database tables to automatically get included when a site runs utf8mb4 conversion

There's an option in the api call / api explorer when running the utf8mb4 conversion to specify some tablename patterns, but this requires the user to know what the tables are that all their extensions create.

One idea is a hook that lets an extension advertise the names of tables it creates. If it wants to manage the charset itself for a table then it can just not list it.

Another is a standard naming like civicrm_ext_FOO, which then core knows not to conflict for its own tables, but which starts with civicrm so gets picked up by default.

Open to other ideas. The status quo is also technically an option. And it's only important if there's some connection between text data in the extension's tables and core tables, or it stores emojis and such.