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/repository/execution/queue.go

@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/zitadel/zitadel/internal/eventstore"
+	"github.com/zitadel/zitadel/internal/execution/target"
 )
 
 const (
@@ -21,6 +22,26 @@ type Request struct {
 	TargetsData []byte                `json:"targetsData"`
 }
 
+func NewRequest(e eventstore.Event, targets []target.Target) (*Request, error) {
+	targetsData, err := json.Marshal(targets)
+	if err != nil {
+		return nil, err
+	}
+	eventData, err := json.Marshal(e)
+	if err != nil {
+		return nil, err
+	}
+	return &Request{
+		Aggregate:   e.Aggregate(),
+		Sequence:    e.Sequence(),
+		EventType:   e.Type(),
+		CreatedAt:   e.CreatedAt(),
+		UserID:      e.Creator(),
+		EventData:   eventData,
+		TargetsData: targetsData,
+	}, nil
+}
+
 func (e *Request) Kind() string {
 	return "execution_request"
 }