[BUG] Data source single selectable/readonly should truncate button text

[BionIT]

Describe the bug
When having a very long option inside data source selectable component, the default icon is gone
We should truncate the text displayed as selected as well

Expected behavior
We should truncate the text and show default icon for the default data source

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

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[BionIT]

This issue has been fixed