libexec/rc/rc.d/Makefile: Use CONFGROUPS.yes

Replace .if statements with CONFGROUPS.${MK_FOO} where possible,
and also sort and re-indent the file for readability.

A couple of more complicated sections don't work with CONFGROUPS.yes
yet, so leave those as they are for now.

MFC after: 1 week
Reviewed by: imp
Sponsored by: https://www.patreon.com/bsdivy
Differential Revision: https://reviews.freebsd.org/D52974