[feat:] Add --wait Flag to doctl databases migrate Command

[SkySingh04]

This PR enhances the doctl databases migrate command by adding a --wait flag. The flag allows users to wait for the migration process to complete, simplifying script automation and removing the need for users to implement their own polling mechanisms.

Changes Made

1. Feature Implementation:

   • Updated the RunDatabaseMigrate function to support the --wait flag.
   • Added logic to poll the /v2/databases/$DATABASE_ID endpoint until the status attribute moves from "migrating" to "online".
   • Display messages (notice) to inform users when the migration is in progress and when it completes.

2. Unit Tests:

   • Enhanced the TestDatabaseMigrate function to include a test case for the --wait flag.
   • Mocked the Get method to simulate database status polling.
   • Ensured the function correctly handles both success and error cases when the --wait flag is used.

Checklist

• Implemented the --wait flag for the RunDatabaseMigrate function.
• Updated the unit tests to cover the --wait flag functionality.
• Verified that all tests pass and that the new feature works as expected.

Related Issue

Fixes: #1584

[SkySingh04]

@loosla Kindly review this PR and let me know if any changes are required

[loosla]

🚀 Awesome job! Thank you for taking the initiative and completing the task!