Redesign of API Readiness App to improve usability and address gaps in engagement experience data model

The API readiness milestone app currently requires a user to go through all steps, which is not always necessary. The GitHub toolchain drives the API Review process via the API Spec pull request (PR). The API readiness milestone should be used to validate that the checks and approvers needed to begin the SDK pre-release work have been completed. These checks/approvers should also be requirements to merge the PR.

- Management plane: Hide the steps: Cleanup validation errors, review breaking changes, Preview API docs, and ARM API Review. These steps should be handled by the spec PR itself. The Sign off step currently shows the status of those checks. We can probably just show that.
- Data plane: Hide the steps: Cleanup spec validation errors and Set up API preview docs. Same reason as for management plane

Relevant GitHub issues:

- [ ] https://github.com/Azure/azure-sdk-tools/issues/7936
- [ ] https://github.com/Azure/azure-sdk-tools/issues/7351
- [ ] https://github.com/Azure/azure-sdk-tools/issues/8632

This work item is related to this epic. https://github.com/Azure/azure-sdk-tools/issues/5670

Start with the API readiness milestone app and compare its management-plane and data-plane step flows with issues 7936, 7351, and 8632. Confirm which checks and approvers must remain visible and required for merging the spec PR; done means unnecessary steps are hidden and the Sign off status covers the required checks.

Written by the indexing model from the issue text.