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 <46600784+stebenz@users.noreply.github.com>
(cherry picked from commit a9ebc06c77)

internal/execution/target/target.go

@@ -0,0 +1,50 @@
+package target
+
+import (
+	"time"
+
+	"github.com/zitadel/zitadel/internal/crypto"
+)
+
+type TargetType uint
+
+const (
+	TargetTypeWebhook TargetType = iota
+	TargetTypeCall
+	TargetTypeAsync
+)
+
+type Target struct {
+	ExecutionID      string              `json:"execution_id,omitempty"`
+	TargetID         string              `json:"target_id,omitempty"`
+	TargetType       TargetType          `json:"target_type,omitempty"`
+	Endpoint         string              `json:"endpoint,omitempty"`
+	Timeout          time.Duration       `json:"timeout,omitempty"`
+	InterruptOnError bool                `json:"interrupt_on_error,omitempty"`
+	SigningKey       *crypto.CryptoValue `json:"signing_key,omitempty"`
+}
+
+func (e *Target) GetExecutionID() string {
+	return e.ExecutionID
+}
+func (e *Target) GetTargetID() string {
+	return e.TargetID
+}
+func (e *Target) IsInterruptOnError() bool {
+	return e.InterruptOnError
+}
+func (e *Target) GetEndpoint() string {
+	return e.Endpoint
+}
+func (e *Target) GetTargetType() TargetType {
+	return e.TargetType
+}
+func (e *Target) GetTimeout() time.Duration {
+	return e.Timeout
+}
+func (e *Target) GetSigningKey(alg crypto.EncryptionAlgorithm) (string, error) {
+	if e.SigningKey == nil {
+		return "", nil
+	}
+	return crypto.DecryptString(e.SigningKey, alg)
+}