[Workspace] Migrate tenant data to workspace

[Hailong-am]

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Is your feature request related to a problem? Please describe.

As workspace and multi-tenancy are mutually exclusive, they can't turn on at the same time.

Data is inside of a tenant cannot be accessed when multi-tenancy is disabled. We need find out a way to help users migrate tenant data to workspace

Describe the solution you'd like

Describe alternatives you've considered

As a workaround, user can export all saved objects from saved objects page under Management/Dashboards Management before turn on workspace and import it to workspace afterwards.

Additional context

https://github.com/opensearch-project/security-dashboards-plugin/pull/1822 opensearch-project/OpenSearch-Dashboards#4944