[ADD] monitoring_prometheus_queue_job

This commit features a refactoring of monitoring_prometheus to get a
cron gathering some metrics from the database, and then publishing the
result on the /metrics endpoint

The new module monitoring_prometheus_queue_job extends the cron to get
information about the queue job states.

setup/monitoring_prometheus_queue_job/setup.py

@@ -0,0 +1,6 @@
+import setuptools
+
+setuptools.setup(
+    setup_requires=['setuptools-odoo'],
+    odoo_addon=True,
+)