systemd-hwdb: convert to VERB_COMMAND and add --introspect-cli

The custom help() is replaced by a COMMAND() description, and
--introspect-cli is added.

test/units/TEST-74-AUX-UTILS.introspect-cli.sh

@@ -17,6 +17,7 @@ INTROSPECTABLE=(
     systemd-backlight
     systemd-dissect
     systemd-firstboot
+    systemd-hwdb
     systemd-id128
     systemd-notify
     systemd-veritysetup
@@ -36,6 +37,12 @@ for i in "${INTROSPECTABLE[@]}"; do
     $i --intro | grep -e --help
 done
 
+# systemd-hwdb defines verbs, check that they are described
+if command -v systemd-hwdb >/dev/null; then
+    systemd-hwdb --introspect-cli | jq -e \
+            '.commands[0].verbs | map(.names[0]) | contains(["query", "update"])'
+fi
+
 # systemd-id128 defines verbs, check that they are described
 systemd-id128 --introspect-cli | jq -e \
     '.commands[0].verbs | map(.names[0]) | contains(["new", "machine-id", "show", "help"])'