refactor(coderd/schedule): move cron schedule to cron package (#9507)

This removes an indirect import of `coderd/database` from the CLI and
results in a logical separation between server related and generalized
schedule.

No size change (yet).

Ref: #9380

coderd/workspaces.go

@@ -22,7 +22,7 @@ import (
 	"github.com/coder/coder/v2/coderd/httpapi"
 	"github.com/coder/coder/v2/coderd/httpmw"
 	"github.com/coder/coder/v2/coderd/rbac"
-	"github.com/coder/coder/v2/coderd/schedule"
+	"github.com/coder/coder/v2/coderd/schedule/cron"
 	"github.com/coder/coder/v2/coderd/searchquery"
 	"github.com/coder/coder/v2/coderd/telemetry"
 	"github.com/coder/coder/v2/coderd/util/ptr"
@@ -1306,7 +1306,7 @@ func validWorkspaceSchedule(s *string) (sql.NullString, error) {
 		return sql.NullString{}, nil
 	}
 
-	_, err := schedule.Weekly(*s)
+	_, err := cron.Weekly(*s)
 	if err != nil {
 		return sql.NullString{}, err
 	}