Port all Celery worker functions to discrete pkg

Moves all tasks run by the Celery worker into a discrete package/module
for easier installation. Also adjusts several parameters throughout to
accomplish this.

worker-daemon/pvcworkerd.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+# pvcworkerd.py - API Celery worker daemon startup stub
+# Part of the Parallel Virtual Cluster (PVC) system
+#
+#    Copyright (C) 2018-2022 Joshua M. Boniface <joshua@boniface.me>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation, version 3.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+###############################################################################
+
+CELERY_BIN="$( which celery )"
+
+# This absolute hackery is needed because Celery got the bright idea to change how their
+# app arguments work in a non-backwards-compatible way with Celery 5.
+case "$( cat /etc/debian_version )" in
+    10.*)
+        CELERY_ARGS="worker --app pvcworkerd.Daemon.celery --events --concurrency 3 --hostname pvcworkerd@$(hostname -s) --queues $(hostname -s) --loglevel INFO"
+    ;;
+    *)
+        CELERY_ARGS="--app pvcworkerd.Daemon.celery worker --events --concurrency 3 --hostname pvcworkerd@$(hostname -s) --queues $(hostname -s) --loglevel INFO"
+    ;;
+esac
+
+${CELERY_BIN} ${CELERY_ARGS}
+exit $?