Which issue(s) does this change fix?

Add support for using sam to test multi-tenancy function.

Why is this change necessary?

AWS Lambda Multi-Tenancy is a new capability for customers who need compute isolation between tenants. Without SAM CLI support, developers can't test tenant-specific business logic locally and has to be forced on cloud deployment for every test iteration which is slow and expensive.

How does it address the issue?

1. Added --tenant-id CLI option across SAM Commands(local invoke, local start-api, local start-lambda, remote invoke)
2. Local Emulation Integration: Passes tenant-id to Runtime Interface Emulator (RIE) via HTTP headers
3. Context Population: RIE/RIC integration ensures context.tenant_id is available in function code

What side effects does this change have?

N/A

Mandatory Checklist

PRs will only be reviewed after checklist is complete

• Review the generative AI contribution guidelines
• Add input/output type hints to new functions/methods
• Write design document if needed (Do I need to write a design document?)
• Write/update unit tests
• Write/update integration tests
• Write/update functional tests if needed
• make pr passes
• make update-reproducible-reqs if dependencies were changed
• Write documentation

Integ test run result: https://github.com/aws/aws-sam-cli/actions/runs/19521003736
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.