Split Debian package into vpp-maglevd + vpp-maglev; add maglevt.1 manpage

vpp-maglevd ships maglevd, maglevd-frontend, both systemd units, and
the config conffiles. vpp-maglev ships maglevc and maglevt as pure
client tools so jump hosts and workstations can install them without
pulling in the daemon. pkg-deb now emits four .debs per release
(2 packages x 2 archs); build-deb.sh takes a package-name argument
and dispatches accordingly.

debian/vpp-maglevd.control.in

@@ -0,0 +1,21 @@
+Package: vpp-maglevd
+Version: @VERSION@
+Architecture: @ARCH@
+Maintainer: Pim van Pelt <pim@ipng.ch>
+Section: net
+Priority: optional
+Depends: systemd, adduser
+Recommends: vpp-maglev
+Description: Maglev health-checker daemon and web frontend for the VPP lb plugin
+ maglevd monitors backends (HTTP, TCP, ICMP) with a rise/fall counter
+ model, programs the VPP lb plugin via its binary API, and exposes the
+ result over a gRPC API and Prometheus metrics endpoint. Configuration
+ is loaded from a YAML file and supports live reload via SIGHUP.
+ .
+ maglevd-frontend is an optional web dashboard that fans one or more
+ maglevd gRPC streams out to browsers over Server-Sent Events. It is
+ installed but not enabled by default; enable with:
+   systemctl enable --now vpp-maglev-frontend
+ .
+ The maglevc CLI client and the maglevt out-of-band tester live in
+ the vpp-maglev package (recommended but not required).