feat: add support for new alertmanager interfaces in grafana

[keithf4]

Description

Add support for the new Alertmanager API interface in Grafana. Automatically provisions a new alertmanager and associates that with the Prometheus datasource.

Ran into an issue with the association not working in 9.5 when testing there, but it works in 9.2 :confused: https://community.grafana.com/t/prometheus-alertmanager-association-missing-in-9-5/102703

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

• [ ] Bugfix
• [x] Enhancement
• [ ] Breaking Change
• [ ] Documentation

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

closes #250

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:
  • [x] OS package repository, distro, and version: Grafana 9.2 from public repo, 9.5 from S3
  • [ ] Local package server, version:
  • [ ] Custom-built package, version:
  • [ ] Other:
• [ ] PostgreSQL, Specify version(s):
• [ ] docs tested with hugo version(s):

Code testing

Have you tested your changes against:

• [x] 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
• [x] Not applicable

If your code touches node_exporter, have you:

• [ ] Ensure that exporter runs with no scrape errors
• [x] 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
• [x] Not applicable

If your code touches Grafana, have you:

• [ ] Ensured Grafana runs without issue
• [ ] Ensured relevant dashboards load without issue
• [x] Not applicable

Checklist:

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