[RAC] Confirm empty state for the alerts table (might be fixed by EUIDataGrid)

[jasonrhodes]

The Alerts Table needs to be able to handle no data state in a graceful way. We need to confirm this is the case with design/product.

[mdefazio]

I think there's likely more we can do here, but these are at least cleaned up mocks from how the current loading / empty state is shown.

Some questions:

• What are our options with the virtualization of the EUIDataGrid?
  • Are we able to show the grid lines, and then perhaps the text loading component within the cell?
• Should this be better addressed at the component level in EUI?

Figma file

Also included in #106585