Create WebhookManager for registration

Problem/Motivation

Create a WebhookManager service in the submodule.
It should handle the webhook lifecycle in one place:

• register
• deregister
• sync
• ping
• rotate

This avoids duplicating logic across hooks, the admin UI, and Drush.
As a developer, I want a WebhookManager service in the submodule.
The service should centralize all DAM webhook orchestration.

Acceptance criteria

• registerAll(bool $force = FALSE): array
  • Registers per event type.
  • Skips stored IDs unless $force is TRUE.
  • Stores IDs in acquia_dam_webhooks.webhook_ids State key.
• deregisterAll(): void
  • Performs a best-effort DELETE for each stored ID.
  • Deletes acquia_dam_webhooks.webhook_ids and all acquia_dam_webhooks.webhook_secret.* State keys.
• syncFromDam(): array
  • Reconciles stored IDs with listWebhooks() response.
  • Re-registers missing webhooks.
    • Returns ['ok', 'repaired', 'failed'].
    • pingAll(): array
    • Returns [event_type => bool].
  • getOrCreateSecret(string $event_type): string
    • Generates bin2hex(random_bytes(32)).
    • Stores the secret in State.
  • rotateAndReregister(): void
    • Clears secrets and IDs.
    • Calls registerAll().
  • getDeliveryUrl(): string
    • Uses Url::fromRoute('acquia_dam_webhooks.webhook_receiver', [], ['absolute' => TRUE]).
  • getStoredWebhookIds(): array
    • Reads State.
  • Service registration
    • Service must be registered as acquia_dam_webhooks.webhook_manager.
    • Constructor injects AcquiaDamWebhookClient, not AcquiaDamClientFactory directly.
    • All DAM webhook API calls must route through acquia_dam_webhooks.api_client.