fix(login): improve auth handlers (#7969)

# Which Problems Are Solved

During the implementation of #7486 it was noticed, that projections in
the `auth` database schema could be blocked.
Investigations suggested, that this is due to the use of
[GORM](https://gorm.io/index.html) and it's inability to use an existing
(sql) transaction.
With the improved / simplified handling (see below) there should also be
a minimal improvement in performance, resp. reduced database update
statements.

# How the Problems Are Solved

The handlers in `auth` are exchanged to proper (sql) statements and gorm
usage is removed for any writing part.
To further improve / simplify the handling of the users, a new
`auth.users3` table is created, where only attributes are handled, which
are not yet available from the `projections.users`,
`projections.login_name` and `projections.user_auth_methods` do not
provide. This reduces the events handled in that specific handler by a
lot.

# Additional Changes

None

# Additional Context

relates to #7486

cmd/setup/26.go

@@ -0,0 +1,27 @@
+package setup
+
+import (
+	"context"
+	_ "embed"
+
+	"github.com/zitadel/zitadel/internal/database"
+	"github.com/zitadel/zitadel/internal/eventstore"
+)
+
+var (
+	//go:embed 26.sql
+	authUsers3 string
+)
+
+type AuthUsers3 struct {
+	dbClient *database.DB
+}
+
+func (mig *AuthUsers3) Execute(ctx context.Context, _ eventstore.Event) error {
+	_, err := mig.dbClient.ExecContext(ctx, authUsers3)
+	return err
+}
+
+func (mig *AuthUsers3) String() string {
+	return "26_auth_users3"
+}