[Feature] support new alert rule (v2) format

## Problem statement

The new rule engine has a lot more functionality, and should allow us to support a wider range of rule migrations.

## Proposed change

When the new alerting framework goes GA, we should output rules in the new format.

## Source system / target system impact

Currently unknown.

## Alternatives considered

N/A

## Additional context

No files, tests, or entry points are identified. First determine the new alerting framework's GA rule format and how current migrations represent alert rules. Done means migrations emit rules in the new format, with source and target impacts clarified and coverage for the supported rule migrations.

Written by the indexing model from the issue text.