fix(eventstore): prevent allocation of filtered events (#6749)

* fix(eventstore): prevent allocation of filtered events

Directly reduce each event obtained from a sql.Rows scan,
so that we do not have to allocate all events in a slice.

* reinstate the mutex as RWMutex

* scan data directly

* add todos

* fix(writemodels): add reduce of parent

* test: remove comment

* update comments

---------

Co-authored-by: adlerhurst <silvan.reusser@gmail.com>

internal/command/preparation/command.go

@@ -25,6 +25,8 @@ var (
 )
 
 // PrepareCommands checks the passed validations and if ok creates the commands
+//
+// Deprecated: filter causes unneeded allocation. Use [eventstore.FilterToQueryReducer] instead.
 func PrepareCommands(ctx context.Context, filter FilterToQueryReducer, validations ...Validation) (cmds []eventstore.Command, err error) {
 	commanders, err := validate(validations)
 	if err != nil {