fix: Consumption tests fixes

[gavin-aguiar]

Description

The Azure Functions Python worker Linux consumption tests were failing with 401 Unauthorized errors during container specialization. The core problem was authentication failure between the test framework and the Azure Functions host running in Docker containers.

Root Cause:
The test framework was using an old SWT (Simple Web Token) format that newer versions of the Azure Functions host no longer accepted
The Azure Functions host had migrated to expecting proper JWT (JSON Web Token) authentication, but the test framework wasn't generating valid JWTs
Issuer/Audience Validation Failures: Even when JWT tokens were attempted, they failed validation due to incorrect issuer and audience claims

Changes Made:

• Added JWT Token Generation
• Fixed Issuer/Audience Format
• Fixed method to download the latest image

Fixes #

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Pull Request Checklist

Host-Worker Contract

• Does this PR impact the host-worker contract (e.g., gRPC messages, shared interfaces)?
  • If yes, have the changes been applied to:
    • azure_functions_worker (Python <= 3.12)
    • proxy_worker (Python >= 3.13)
  • If no, please explain why:

Worker Execution Logic

• Does this PR affect worker execution logic (e.g., function invocation, bindings, lifecycle)?
  If yes, please answer the following:

Python Version Coverage

• Does this change apply to both Python <=3.12 and 3.13+?
• If yes, have the changes been made to:
  • azure_functions_worker (Python <= 3.12)
  • azure_functions_worker_v1 / azure_functions_worker_v2 (Python >= 3.13)
• If no, please explain why:

Programming Model Compatibility (for Python 3.13+)

• Does this change apply to both:
  • V1 programming model (azure_functions_worker_v1)?
  • V2 programming model (azure_functions_worker_v2)?
• Explanation (if limited to one model):