Fix integration test failures for multi-tenancy

[licjun]

We saw several integ test failures when merging in the change for multi-tenancy.

Failure #1 Resource Conflict
In remote invoke integ test, we saw failure like this.
tests/integration/remote/invoke/test_remote_invoke.py::TestSingleLambdaInvoke::test_invoke_asynchronous_using_boto_parameter@sam_remote_invoke_single_lambda_resource - AssertionError: 0 != 1

This is due to we added a MultiTenantFunction in the existing template which has a HelloWorldFunction, and when doing remote invoke, we use command like this sam remote invoke --stack-name TestSingleLambdaInvoke-abc123, sam can't decide which function to invoke, so it failed. The solution is to create a separate template for multi-tenant test.

Failure #2 Line number mismatch
in test_integrations_cli.py, we saw error like this
Error: tests/integration/local/invoke/test_integrations_cli.py::TestInvokeFunctionWithError::test_function_exception - AssertionError: '\xa0\xa0File "/var/task/main.py", line 51, in raise_exception' not found in '2025-11-20 00:45:25 Attaching import module proxy for analyzing dynamic imports\nInvoking main.raise_exception (python3.11)\nLocal image is up-to-date\nUsing local image: public.ecr.aws/lambda/python:3.11-rapid-x86_64.\n\nMounting /home/runner/work/aws-sam-cli/aws-sam-cli/tests/integration/testdata/invoke as /var/task:ro,delegated, the reason is multi-tenancy change added code to the tests/integration/testdata/invoke/main.py file, which shifted the line numbers.

Failure #3
In test_start_api.py, we saw error like
tests/integration/local/start_api/test_start_api.py::TestStartApiWithStage::test_default_stage_name - AssertionError: None != 'Prod', this is due to we added a new MultiTenantFunction with its own Type: Api in the existing template which has global Api configuration, this conflict causes the failure, the fix is to create a separate template for multi-tenant tests.

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

[roger-zhangg]

https://github.com/aws/aws-sam-cli/actions/runs/19525062770