Use global lock for auth credential access in tests.

Problem

We have at least two tests that are using Amplify Auth to get Cognito credentials. There's a lock guarding access to Amplify Auth apis. However, these tests are using separate factory instances due to different configuration and effectively two separate locks. This is wrong, because Amplify Auth apis need global locking (they're static, i.e. attached to global session).

This sometimes results in errors like this:

https://github.com/aws-amplify/amplify-backend/actions/runs/10964134931/job/30447221560

test at file:/Users/runner/work/amplify-backend/amplify-backend/packages/integration-tests/lib/test-e2e/sandbox.test.js:41:26
✖ generates config after sandbox --once deployment (22038.52175ms)
  NotAuthorizedException: Invalid session for the user.
      at <anonymous> (/Users/runner/work/amplify-backend/amplify-backend/node_modules/@aws-amplify/auth/src/providers/cognito/utils/clients/CognitoIdentityProvider/index.ts:18:19)
      at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
      at Module.confirmSignIn (/Users/runner/work/amplify-backend/amplify-backend/node_modules/@aws-amplify/auth/src/providers/cognito/apis/confirmSignIn.ts:53:138)
      at AmplifyAuthCredentialsFactory.getNewAuthenticatedUserCredentials (/Users/runner/work/amplify-backend/amplify-backend/packages/integration-tests/src/amplify_auth_credentials_factory.ts:88:7)
      at ConversationHandlerTestProject.assertPostDeployment (/Users/runner/work/amplify-backend/amplify-backend/packages/integration-tests/src/test-project-setup/conversation_handler_project.ts:165:7)
      at TestContext.<anonymous> (/Users/runner/work/amplify-backend/amplify-backend/packages/integration-tests/src/test-e2e/sandbox.test.ts:77:13)
      at async Test.run (node:internal/test_runner/test:632:9)
      at async Suite.processPendingSubtests (node:internal/test_runner/test:374:7) {
    underlyingError: undefined,
    recoverySuggestion: undefined
  }

Changes

Make lock global to match Amplify Auth api scope.

Validation

PR checks with e2e.

Checklist

[ ] If this PR includes a functional change to the runtime behavior of the code, I have added or updated automated test coverage for this change.
[ ] If this PR requires a change to the Project Architecture README, I have included that update in this PR.
[ ] If this PR requires a docs update, I have linked to that docs PR above.
[ ] If this PR modifies E2E tests, makes changes to resource provisioning, or makes SDK calls, I have run the PR checks with the run-e2e label set.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

aws-amplify / amplify-backend