* chore: replace artisnal FakeDashboardService with generated mock
Maintaining a handcrafted FakeDashboardService is not sustainable now that we are in the process of moving the dashboard-related functions out of sqlstore.
* sqlstore: finish removing Find and SearchDashboards
Find and SearchDashboards were previously copied into the dashboard service. This commit completes that work, removing Find and SearchDashboards from the sqlstore and updating callers to use the dashboard service.
* dashboards: remove SearchDashboards from Store interface
SearchDashboards is a wrapper around FindDashboard that transforms the results, so it's been moved out of the Store entirely and the functionality moved into the Dashboard Service's search implementation.
The database tests depended heavily on the transformation, so I added testSearchDashboards, a copy of search dashboards, instead of (heavily) refactoring all the tests.
