perf(actionsv2): execution target router (#10564)

# Which Problems Are Solved

The event execution system currently uses a projection handler that
subscribes to and processes all events for all instances. This creates a
high static cost because the system over-fetches event data, handling
many events that are not needed by most instances. This inefficiency is
also reflected in high "rows returned" metrics in the database.

# How the Problems Are Solved

Eliminate the use of a project handler. Instead, events for which
"execution targets" are defined, are directly pushed to the queue by the
eventstore. A Router is populated in the Instance object in the authz
middleware.

- By joining the execution targets to the instance, no additional
queries are needed anymore.
- As part of the instance object, execution targets are now cached as
well.
- Events are queued within the same transaction, giving transactional
guarantees on delivery.
- Uses the "insert many fast` variant of River. Multiple jobs are queued
in a single round-trip to the database.
- Fix compatibility with PostgreSQL 15

# Additional Changes

- The signing key was stored as plain-text in the river job payload in
the DB. This violated our [Secrets
Storage](https://zitadel.com/docs/concepts/architecture/secrets#secrets-storage)
principle. This change removed the field and only uses the encrypted
version of the signing key.
- Fixed the target ordering from descending to ascending.
- Some minor linter warnings on the use of `io.WriteString()`.

# Additional Context

- Introduced in https://github.com/zitadel/zitadel/pull/9249
- Closes https://github.com/zitadel/zitadel/issues/10553
- Closes https://github.com/zitadel/zitadel/issues/9832
- Closes https://github.com/zitadel/zitadel/issues/10372
- Closes https://github.com/zitadel/zitadel/issues/10492

---------

Co-authored-by: Stefan Benz <[email protected]>

internal/queue/migrate.go

@@ -2,27 +2,27 @@ package queue
 
 import (
 	"context"
+	"database/sql"
 
-	"github.com/jackc/pgx/v5"
 	"github.com/riverqueue/river/riverdriver"
-	"github.com/riverqueue/river/riverdriver/riverpgxv5"
+	"github.com/riverqueue/river/riverdriver/riverdatabasesql"
 	"github.com/riverqueue/river/rivermigrate"
 
 	"github.com/zitadel/zitadel/internal/database"
 )
 
 type Migrator struct {
-	driver riverdriver.Driver[pgx.Tx]
+	driver riverdriver.Driver[*sql.Tx]
 }
 
 func NewMigrator(client *database.DB) *Migrator {
 	return &Migrator{
-		driver: riverpgxv5.New(client.Pool),
+		driver: riverdatabasesql.New(client.DB),
 	}
 }
 
 func (m *Migrator) Execute(ctx context.Context) error {
-	_, err := m.driver.GetExecutor().Exec(ctx, "CREATE SCHEMA IF NOT EXISTS "+schema)
+	err := m.driver.GetExecutor().Exec(ctx, "CREATE SCHEMA IF NOT EXISTS "+schema)
 	if err != nil {
 		return err
 	}