Add detail and status to custom metric rows

[noponoponopo]

Context of Contribution

• Bug Fix
• Refactoring
• New Feature
• Others

Summary of the Proposal

This pull request adds two optional fields to each Custom Metrics row:

• detail displays secondary text below the row.
• state displays a colored status indicator using active, waiting, completed, or error.

The fields are optional, so existing Custom Metrics JSON files preserve their current behavior.

A dedicated CustomMetricView keeps the row presentation separate from the card presentation.

All 136 tests pass.

Reason for the new feature

Custom Metrics producers currently need to combine status, value, and supporting context into a single display string.

The optional fields provide a structured way to show concise status information and secondary context. This is useful for sessions, jobs, queues, services, and other metrics where a value alone does not provide enough information.

The maintenance cost is limited to two optional Codable fields, one status enum, and a dedicated row view. Existing JSON files do not require migration.

Checklist

• I have read the CONTRIBUTING.md and agree to follow it.
• This PR does not contain commits of multiple contexts.
• Code follows proper indentation and naming conventions.
• Implemented using only APIs that can be submitted to the App Store.

[Kyome22]

@noponoponopo If there are any changes that significantly affect the visual appearance, please make sure to include appropriate screenshots to showcase them.

Additionally, I intend to handle the custom metrics JSON schema with extreme caution, as any changes once made will have a significant impact. Please be prepared for the fact that requests will not be approved easily.

This also applies to the other pull requests you have created.