Decouple HookTask from Repository (#17940)

At the moment a repository reference is needed for webhooks. With the
upcoming package PR we need to send webhooks without a repository
reference. For example a package is uploaded to an organization. In
theory this enables the usage of webhooks for future user actions.

This PR removes the repository id from `HookTask` and changes how the
hooks are processed (see `services/webhook/deliver.go`). In a follow up
PR I want to remove the usage of the `UniqueQueue´ and replace it with a
normal queue because there is no reason to be unique.

Co-authored-by: 6543 <6543@obermui.de>

routers/api/v1/repo/hook.go

@@ -168,7 +168,7 @@ func TestHook(ctx *context.APIContext) {
 	commit := convert.ToPayloadCommit(ctx.Repo.Repository, ctx.Repo.Commit)
 
 	commitID := ctx.Repo.Commit.ID.String()
-	if err := webhook_service.PrepareWebhook(hook, ctx.Repo.Repository, webhook.HookEventPush, &api.PushPayload{
+	if err := webhook_service.PrepareWebhook(ctx, hook, webhook.HookEventPush, &api.PushPayload{
 		Ref:          ref,
 		Before:       commitID,
 		After:        commitID,