* update AlertingEnabled and UnifiedAlertingSettings.Enabled to be pointers
* add a pseudo migration to fix the AlertingEnabled and UnifiedAlertingSettings.Enabled if the latter is not defined
* update the default configuration file to make default value for both 'enabled' flags be undefined
Misc
* update Migrator to expose DB engine. This is needed for a ualert migration to access the database while the list of migrations is created.
* add more verbose failure when migrations do not match
Co-authored-by: gotjosh <josue@grafana.com>
Co-authored-by: Yuriy Tseretyan <yuriy.tseretyan@grafana.com>
Co-authored-by: gillesdemey <gilles.de.mey@gmail.com>
