enhance(backend): refine system account (#15530)

* wip

* wip

* wip

* Update SystemAccountService.ts

* Update 1740121393164-system-accounts.js

* Update DeleteAccountService.ts

* wip

* wip

* wip

* wip

* Update 1740121393164-system-accounts.js

* Update RepositoryModule.ts

* wip

* wip

* wip

* Update ApRendererService.ts

* wip

* wip

* Update SystemAccountService.ts

* fix tests

* fix tests

* fix tests

* fix tests

* fix tests

* fix tests

* add print logs

* ログが長すぎて出てないかもしれない

* fix migration

* refactor

* fix fed-tests

* Update RelayService.ts

* merge

* Update user.test.ts

* chore: emit log

* fix: tweak sleep duration

* fix: exit 1

* fix: wait for misskey processes to become healthy

* fix: longer sleep for user deletion

* fix: make sleep longer again

* デッドロック解消の試み

https://github.com/misskey-dev/misskey/issues/15005

* Revert "デッドロック解消の試み"

This reverts commit 266141f66f.

* wip

* Update SystemAccountService.ts

---------

Co-authored-by: おさむのひと <46447427+samunohito@users.noreply.github.com>
Co-authored-by: zyoshoka <107108195+zyoshoka@users.noreply.github.com>

packages/backend/test/unit/WebhookTestService.ts

@@ -88,8 +88,8 @@ describe('WebhookTestService', () => {
 	});
 
 	beforeEach(async () => {
-		root = await createUser({ username: 'root', usernameLower: 'root', isRoot: true });
-		alice = await createUser({ username: 'alice', usernameLower: 'alice', isRoot: false });
+		root = await createUser({ username: 'root', usernameLower: 'root' });
+		alice = await createUser({ username: 'alice', usernameLower: 'alice' });
 
 		userWebhookService.fetchWebhooks.mockReturnValue(Promise.resolve([
 			{ id: 'dummy-webhook', active: true, userId: alice.id } as MiWebhook,