feat(eventstore): accept transaction in push (#8945)

# Which Problems Are Solved

Push is not capable of external transactions.

# How the Problems Are Solved

A new function `PushWithClient` is added to the eventstore framework
which allows to pass a client which can either be a `*sql.Client` or
`*sql.Tx` and is used during push.

# Additional Changes

Added interfaces to database package.

# Additional Context

- part of https://github.com/zitadel/zitadel/issues/8931

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

internal/eventstore/v3/eventstore.go

@@ -4,6 +4,7 @@ import (
 	"context"
 
 	"github.com/zitadel/zitadel/internal/database"
+	"github.com/zitadel/zitadel/internal/eventstore"
 )
 
 var (
@@ -11,12 +12,19 @@ var (
 	pushPlaceholderFmt string
 	// uniqueConstraintPlaceholderFmt defines the format of the unique constraint error returned from the database
 	uniqueConstraintPlaceholderFmt string
+
+	_ eventstore.Pusher = (*Eventstore)(nil)
 )
 
 type Eventstore struct {
 	client *database.DB
 }
 
+// Client implements the [eventstore.Pusher]
+func (es *Eventstore) Client() *database.DB {
+	return es.client
+}
+
 func NewEventstore(client *database.DB) *Eventstore {
 	switch client.Type() {
 	case "cockroach":