feat: port vhost proxy :report subcommands to golang

The bash :report implementations for the caddy, haproxy, openresty, and traefik proxy plugins are replaced with a compiled golang binary that collects report keys in parallel and marshals json directly. The traefik dns-provider values keep their masking behaviour, remaining hidden in the default stdout report while surfacing for --format json or an explicit flag query. These four plugins previously had no unit tests, so a bats suite covering the report matrix is added for each.

plugins/haproxy-vhosts/subcommands/report

@@ -1,6 +0,0 @@
-#!/usr/bin/env bash
-source "$PLUGIN_AVAILABLE_PATH/haproxy-vhosts/command-functions"
-set -eo pipefail
-[[ $DOKKU_TRACE ]] && set -x
-
-cmd-haproxy-report "$@"