packages: Rename unbound to local-unbound

This more accurately reflects its purpose, and its contents, since
everything in the package is prefixed with "local-".

While here, add a message on upgrade about regenerating the config.

MFC after:	3 seconds
Requested by:	des
Reviewed by:	des
Sponsored by:	https://www.patreon.com/bsdivy
Differential Revision:	https://reviews.freebsd.org/D53056

etc/Makefile

@@ -68,7 +68,7 @@ distribution:
 # install the /etc/unbound symlink, otherwise, don't overwrite the user's
 # existing symlink.
 	if [ "${NO_ROOT:Dtrue}" = true -o ! -e ${DESTDIR}/etc/unbound ]; then \
-		${INSTALL_SYMLINK} -Tpackage=unbound ../var/unbound \
+		${INSTALL_SYMLINK} -Tpackage=local-unbound ../var/unbound \
 			${DESTDIR}/etc/unbound; \
 	fi
 .endif

etc/mtree/BSD.var.dist

@@ -104,8 +104,8 @@
         vi.recover      mode=01777
         ..
     ..
-    unbound         uname=unbound gname=unbound mode=0755 tags=package=unbound
-        conf.d          uname=unbound gname=unbound mode=0755 tags=package=unbound
+    unbound         uname=unbound gname=unbound mode=0755 tags=package=local-unbound
+        conf.d          uname=unbound gname=unbound mode=0755 tags=package=local-unbound
         ..
     ..
     yp