packages: Move powerd to its own package

[ivy]

Summary

Nearly everyone wants powerd to manage CPU frequency scaling on real
hardware, even if -utilities isn't installed. Conversely, very small
jails might want -utilities but don't need powerd.

Move it to its own package and add it to the minimal set.

MFC after: 3 days

[ivy]

add an UPDATING entry

... although i'm wondering if we should stop doing these after the 15.0 release,
at least for packages which are in set-minimal, since they're quite spammy.

[ivy]

add the missing powerd-all.ucl

[imp]

Spammy how? Unlike ports, UPDATING isn't automatically displayed. I imagine that they'd slow way down once we have the deck chairs just so...

[ivy]

In D52645#1202643, @imp wrote:

Spammy how? Unlike ports, UPDATING isn't automatically displayed. I imagine that they'd slow way down once we have the deck chairs just so...

well, just reading through UPDATING, a lot of recent entries are about pkgbase. but i suppose it's fine, people can just skip them if they aren't interested.