app-admin/supervisor: bump to 3.3.4, add default config, dedicated group

app-admin/supervisor: bump to 3.3.4, add default config, dedicated group

- Add a default configuration file.
- Add a dedicated log directory and a group to which users can be added
in order to run supervisorctl and access logs.
- Fix warnings related to namespace packages.
- Add a missing RDEPEND on dev-python/setuptools (pkg_resources).
- Fix the init script to explicitely specify a configuration file to
supervisord, otherwise a warning is issued.
- Add informational messages when the package is installed for the first
time.

Closes: https://bugs.gentoo.org/589734

Package-Manager: Portage-2.3.31, Repoman-2.3.9
Closes: https://github.com/gentoo/gentoo/pull/8453