added tag retention tasks list subcommand

[NishchayRajput]

Description

Briefly describe what this pull request does and why the change is needed.
This PR adds the harbor tag retention tasks list subcommand to display retention execution tasks for a specific retention policy execution.

It enables users to view and inspect individual tasks from a retention policy execution, showing details such as task ID, repository, status, retention metrics, and timing information.

• Fixes feat: immutable tags update subcommand #802

Type of Change

Please select the relevant type.

• Bug fix
• New feature
• Documentation update
• Refactor
• Chore / maintenance

Changes

• Added harbor tag retention tasks command group under harbor tag retention.
• Added harbor tag retention tasks list [PROJECT_NAME] with:
  • Interactive mode (prompts for project and execution selection if not provided)
  • Flag-based mode with explicit project ID/name and execution ID
  • Table-based output with task details (ID, Execution ID, Repository, Status, Retained, Total, Code, Revision, Start Time, End Time)
  • JSON output format support via --output-format json
• Added retention API helpers:
  • ListRetentionExecutions() - fetch retention executions for a policy
  • ListRetentionTasks() - fetch tasks for a specific execution
• Added UI/View components:
  • RetentionExecutionList() - interactive selection view for executions
  • RetentionTaskList() - task details table view
• Added prompt helpers:
  • GetRetentionExecutionIDFromUser() - interactive execution selection