Support for sql_exporter with pgMonitor extension

[keithf4]

Description

The adds support for the sql_exporter which makes use of the new extension metrics. It requires the pgmonitor-extension found here - https://github.com/CrunchyData/pgmonitor-extension

The extension adds features for

• materialized views for more complicated queries or queries that may run slower (Ex. size)
  • Additional metrics to monitor if refresh ran and for how long
• plain views to define other metrics that need immediate, matview results (replication, connections, etc)
• refreshing of a plain table for more complicated metrics that cannot use a matview (pgbackrest monitoring)

Other new features in 5.0 include

• Add support for collecting metrics directly from PgBouncer instead of requiring the pgbouncer_fdw.
• New Grafana dashboards to support sql_exporter and direct pgBouncer monitoring (instead of using pgbouncer_fdw)
• Add support for alerting on pgmonitor-extension runtime metrics
• Reorganize the Grafana dashboards in the repository to make it easier to individually package the different types of dashboards and only install the ones that are actually in use

Please indicate what kind of change your PR includes (multiple selections are acceptable):

• Bugfix
• Enhancement
• Breaking Change
• Documentation

PRs should be against existing issues, so please list each issue using a separate 'closes' line:

closes #395

If this PR depends on another PR or resolution of another issue, please indicate that here using a separate 'depends' line for each dependency.

depends on #

If you have an external dependency (packages, portal updates, etc), add the 'BLOCKED' tag to your PR.

Testing

None of the testing listed below is optional.

• Installation method:
  • Binary install from source, version:
  • OS package repository, distro, and version:
  • Local package server, version:
  • Custom-built package, version:
  • Other:
• PostgreSQL, Specify version(s): All supported (11-15)
• docs tested with hugo version(s):

Code testing

Have you tested your changes against:

• RedHat/CentOS
• Ubuntu
• SLES
• Not applicable

If your code touches postgres_exporter, have you:

• Tested against all versions of PostgreSQL affected
• Ensure that exporter runs with no scrape errors
• Not applicable

If your code touches node_exporter, have you:

• Ensure that exporter runs with no scrape errors
• Not applicable

If your code touches Prometheus, have you:

• Ensured all configuration changes pass promtool check config
• Ensured all alert rule changes pass promtool check rules
• Prometheus runs without issue
• Alertmanager runs without issue
• Not applicable

If your code touches Grafana, have you:

• Ensured Grafana runs without issue
• Ensured relevant dashboards load without issue
• Not applicable

Checklist:

• I have made corresponding changes to:
  • the documentation
  • the release notes
  • the upgrade doc

[ChuckHend]

👋

[jchancojr]

lgtm