sys-apps/rng-tools: rewrite initd and confd (6.6-r1 only)

sys-apps/rng-tools: rewrite initd and confd (6.6-r1 only)

Restructure the openrc init script and the accompanying confd file to
reflect the recent changes to rngd.

- Instead of having individual NO_FOO="1" style variables in the confd
  file for each entropy source, maintain a single list of entropy
  sources to enable. Likewise, maintain a list of entropy sources to
  disable.
- Allow per-entropy-source options to be set inside the confd file.
- The init file defines $description now.
- Use $command_args_background instead of $command_args to specify the
  daemon behavior.
- Allow default setting of --fill-watermark.
- Allow extra arguments to be passed to rngd from the confd file.

Bug: https://bugs.gentoo.org/650622
Bug: https://bugs.gentoo.org/673120
Package-Manager: Portage-2.3.52, Repoman-2.3.12
Signed-off-by: Göktürk Yüksek <gokturk@gentoo.org>