[BUG] [Workspace]Not able to view legacy data on saved objects page when workspace exists

[Hailong-am]

Describe the bug

When workspace is enabled and no workspace created, goes to saved objects page, user is able to see legacy data(without workspace). But when a new workspace is created, goes to saved objects page again, it will only see saved objects associated with workspace.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior

dashboard admin user should see legacy data no matter whether there has workspace or not

OpenSearch Version
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Dashboards Version
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Plugins

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Screenshots

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Host/Environment (please complete the following information):

• OS: [e.g. iOS]
• Browser and version [e.g. 22]

Additional context

related to #7165
#4944