dev-db/pgagent: new revision with a dedicated "pgagent" user.

dev-db/pgagent: new revision with a dedicated "pgagent" user.

The pgagent daemon used to run as root, which can be dangerous. That
system user is used to execute the database jobs, meaning that a
non-root user with permission to schedule pgagent jobs could gain
root. This new revision creates a dedicated "pgagent" system user,
and the new init script launches the daemon as that user.

An ewarn lets users know that some migration work may be needed.

Gentoo-Bug: 537264

Package-Manager: Portage-2.3.6, Repoman-2.3.1