feat: grafana-ha

[UnicornChance]

Description

• Document the HA setup requirements for Grafana.
• Ensure that these are provided as an example configuration.
• Setup the nightly testing with an external RDS database to ensure this is consistently tested in nightly CI.
• Update task for testing HA configuration locally to utilize single postgres docker container for keycloak and grafana.

To Test

1. utilize the test-uds-core-ha task to deploy HA grafana and keycloak.
2. after deployment, access grafana dashboard at grafana.admin.uds.dev and validate things are working.
3. make sure there is scaled grafana pods ( should be 2 pods ).
4. add a dashboard to grafana ui.
5. delete pods and validate dashboard still exists.

Related Issue

Fixes #716

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Other (security config, docs update, etc)

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide followed