This proved to be helpful for previous protocol experiments, so let's
upstream it. Inspired by the corresponding code in Weston.
Protocols need to be placed in a `protocols` subdirectory and can be
declared in the following way in `meson.build`:
```
['color-management-v1', 'internal' ],
```
Note the `v1` being part of the name.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9186>