Flows: Extend DatasetPermissions GraphQL type with canSchedule flag

[zaychenko-sergei]

Currently dataset permission structure for UI consist of the following control flags:

type DatasetPermissions {
  canView: Boolean!
  canDelete: Boolean!
  canRename: Boolean!
  canCommit: Boolean!
}

Add one more flag for scheduling permissions, canSchedule, which should control:

• ability to manually trigger dataset update action
• ability to modify dataset scheduling permissions
• ability to cancel scheduled dataset update task