Improve formatting of synopsis section

This patch is about sorting the arguments and using proper mdoc(7) macros
to stylize arguments and command modifiers for much better readability.

Further style fixes in other sections within the bhyve manual page are
going to be worked on in upcoming patches.

Reviewed by:	rgrimes
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D24526

usr.sbin/bhyve/bhyve.8

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 13, 2019
+.Dd April 22, 2020
 .Dt BHYVE 8
 .Os
 .Sh NAME
@@ -32,23 +32,40 @@
 .Nd "run a guest operating system inside a virtual machine"
 .Sh SYNOPSIS
 .Nm
-.Op Fl abehuwxACHPSWY
+.Op Fl AabCeHhPSuWwxY
 .Oo
-.Fl c\~ Ns
+.Sm off
+.Fl c\~
 .Oo
-.Op Ar cpus= Ns
-.Ar numcpus Ns
-.Oc Ns
-.Op Ar ,sockets=n Ns
-.Op Ar ,cores=n Ns
-.Op Ar ,threads=n
+.Op Cm cpus=
+.Ar numcpus
 .Oc
-.Op Fl g Ar gdbport
-.Op Fl l Ar help|lpcdev Ns Op , Ns Ar conf
-.Op Fl m Ar memsize Ns Op Ar K|k|M|m|G|g|T|t
-.Op Fl p Ar vcpu:hostcpu
-.Op Fl s Ar help|slot,emulation Ns Op , Ns Ar conf
+.Op Cm ,sockets= Ar n
+.Op Cm ,cores= Ar n
+.Op Cm ,threads= Ar n
+.Oc
+.Sm on
 .Op Fl G Ar port
+.Op Fl g Ar gdbport
+.Oo Fl l
+.Sm off
+.Cm help | Ar lpcdev Op Cm \&, Ar conf
+.Sm on
+.Oc
+.Oo Fl m
+.Sm off
+.Ar memsize
+.Oo
+.Cm K No | Cm k No | Cm M No | Cm m No | Cm G No | Cm g No | Cm T No | Cm t
+.Oc
+.Sm on
+.Oc
+.Op Fl p Ar vcpu Ns Cm \&: Ns Ar hostcpu
+.Oo Fl s
+.Sm off
+.Cm help | Ar slot Cm \&, Ar emulation Op Cm \&, Ar conf
+.Sm on
+.Oc
 .Op Fl U Ar uuid
 .Ar vmname
 .Sh DESCRIPTION