Review new v29 Prometheus release and establish what's required to use

[ChrisMcGowan]

The new v29 series of prometheus BOSH release has switched it's metrics input to the new style CF metrics.

Currently we are using the legacy Firehose based metrics.

Notes

• Review the breaking changes to see what has to change in our prometheus deployment repo
• What changes need to be made in our CF deployment repo

Acceptance Criteria

• Review changes that need to be made to cg-deploy-prometheus to use new style metrics
• Review changes that need to be made to cg-deploy-cf to emit the new style metrics if not already being emitted
• Create tickets to update cg-deploy-cf as needed for changes

[ChrisMcGowan]

Staging work testing is complete.

Staging is reverted back to normal deployment

Draft PR for new ADR on path moving forward is ready for peer review: https://github.com/cloud-gov/internal-docs/pull/230

[ChrisMcGowan]

ADR approved and merged

New ticket for doing the updates in and tentative schedule for PI 39.3: #239