Fix bad query in findAllWorkspaceAndInstances

[geropl]

This issue was brought up again by this change. We hotfixed the query on the client side with this commit.

After investigation during https://app.incident.io/incidents/217 we found the root cause:

SELECT COUNT(DISTINCT `ws`.`id`) AS `cnt`
    FROM `d_b_workspace` `ws`
        INNER JOIN `d_b_workspace_instance` `wsi`
            ON `wsi`.`id` = (SELECT i.id FROM d_b_workspace_instance AS i WHERE i.workspaceId = `ws`.`id` ORDER BY i.creationTime DESC LIMIT 1)

It's issued from this method. Specifically, the getCount call here is the expensive one.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.