[Retiarii] support experiment view and resume

[QuanluZhang]

Description

• [x] Retiarii experiment view using python API
• [x] Retiarii experiment view using nnictl
• [x] Retiarii experiment resume using python API
• [x] Retiarii experiment resume using nnictl

Test Options

• [ ] fast test
• [ ] full test - HPO
• [ ] full test - NAS
• [ ] full test - compression

Checklist

• [x] test case
• [x] doc

How to test