feat(ws): Implement Start restart and stop workspace actions

[ElayAharoni]

Fixes: #146

Implemented Start, restart and stop workspace actions present in the workspace table actions kebab dropdown.
with the requested buttons and warning, from the issue description.
snapshots:

1. start with pending updates:
   

2. restart without pending updates:
   

3. stop without pending updates:
   

4. stop with pending updates:
   

5. restart with pending updates:
   

[google-oss-prow]

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[paulovmr]

Hi @ElayAharoni , thanks for the PR. IMO, we should have one component (and its .tsx file) for each of those modals, instead of managing UI features as React states. This way each component would be isolated and could call the appropriate BFF service to execute its action. In the Workspaces.tsx, we would have only the const [isXModalOpen, setIsXModalOpen] = React.useState(false); boolean state to manage if each popup is opened or not.

This idea is similar to what Model Registry does with ModelVersionsTableRow using the ArchiveModelVersionModal modal.