feat: 'data:pg:migrate' interactive method selection (W-22585064)

[sbosio]

Summary

Adds an interactive prompt to the data:pg:migrate command that allows users to select a migration method (Snapshot or Streaming) when configuring a database migration. The prompt includes descriptions of each method to help users make an informed choice. When the --method flag is provided, the interactive prompt is skipped.

Type of Change

Feature Additions (minor semver update)

• feat: Introduces a new feature to the codebase

Testing

Notes:

• The --method flag no longer has a default value to enable detection of interactive vs. flag-based flow
• Existing tests updated to explicitly pass --method=snapshot to maintain their original behavior
• New test suite added to cover interactive method selection scenarios

Steps:

1. Checkout this branch and run npm install && npm run build
2. Run ./bin/run data:pg:migrate --app=<app-name> without the --method flag. The app is required to have at least two migreable Classic databases (standard-0 or higher, not Essential-tier).
3. Select a source database
4. Create a new database as target
5. Verify the method selection prompt appears with Snapshot and Streaming options
6. Select method and confirm the migration configuration
7. Run ./bin/run data:pg:migrate --app=<app-name> --method=snapshot and verify the method prompt is skipped

Related Issues

GUS work item: W-22585064

[tlowrimore-heroku]

LGTM!

[sbosio]

Do not merge yet. We'll be merging after @heicheng18 has reviewed the new strings introduced for the feature.