List the SqlInstance available settings.

**Reasoning**
As part of our build pipeline, we would like to warn users about expected SqlInstance restart if specific settings or database flags values have been changed.

**Expected solution**
I would like to be able to list the available settings for SqlInstance with their description similar to the currently available listing of Database Flags.

**Describe alternatives you've considered**
Currently, we statically store these settings in our app's configuration.

**Additional context**
current available database flags can be fetched using `SqlAdmin.flags().list()`, something similar like `SqlAdmin.instance.settings.list` to list SqlInstance settings would be very much appreciated