feat(eventstore): increase parallel write capabilities (#5940)

This implementation increases parallel write capabilities of the eventstore.
Please have a look at the technical advisories: [05](https://zitadel.com/docs/support/advisory/a10005) and  [06](https://zitadel.com/docs/support/advisory/a10006).
The implementation of eventstore.push is rewritten and stored events are migrated to a new table `eventstore.events2`.
If you are using cockroach: make sure that the database user of ZITADEL has `VIEWACTIVITY` grant. This is used to query events.

internal/eventstore/v3/eventstore.go

@@ -0,0 +1,29 @@
+package eventstore
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/internal/database"
+)
+
+// pushPlaceholderFmt defines how data are inserted into the events table
+var pushPlaceholderFmt string
+
+type Eventstore struct {
+	client *database.DB
+}
+
+func NewEventstore(client *database.DB) *Eventstore {
+	switch client.Type() {
+	case "cockroach":
+		pushPlaceholderFmt = "($%d, $%d, $%d, $%d, $%d, $%d, $%d, $%d, $%d, hlc_to_timestamp(cluster_logical_timestamp()), cluster_logical_timestamp(), $%d)"
+	case "postgres":
+		pushPlaceholderFmt = "($%d, $%d, $%d, $%d, $%d, $%d, $%d, $%d, $%d, statement_timestamp(), EXTRACT(EPOCH FROM clock_timestamp()), $%d)"
+	}
+
+	return &Eventstore{client: client}
+}
+
+func (es *Eventstore) Health(ctx context.Context) error {
+	return es.client.PingContext(ctx)
+}