feature: provide model service validation

[lizable]

This PR resolves #2058. Related: backend.ai#1754

⚠️ NOTE: you need to change the core branch to related PR.

• [x] Check the result of validation changes when click validate button (processing... -> finished)
• [x] Check you can execute "real" service when validation is on processing
• [x] Check you can validate service only if the model-definition file is in model-usage vfolder (refer here)
• [x] Check you can see the container log clearly after clicking validate button.

Checklist: (if applicable)

• [x] Mention to the original issue
• [ ] Documentation
• [x] Minimum required manager version
• [ ] Specific setting for review (eg., KB link, endpoint or how to setup)
• [x] Minimum requirements to check during review
• [ ] Test case(s) to demonstrate the difference of before/after

Screenshot(s)