fix: move pip authenticate to first step for all pipelines

[hallvictoria]

Description

The UsePythonVersion@0 task installs and upgrades pip - with the recent networking changes, this step will fail when the agent tries to install pip from pypi.org. This change moves the internal feed authentication task (PipAuthenticate) to always be the first step in all pipelines, so that whenever pip is installed, it's installed from the internal feed.

(previous) Example run: https://azfunc.visualstudio.com/internal/_build/results?buildId=292394&view=logs&j=444070dd-ff9b-522a-cc83-036544755457&t=339617d4-cdaa-5df9-bfd2-12ddd87b7576 - UsePythonVersion@0 installs pip from pypi.org

(previous) Example failure: https://dev.azure.com/azfunc/internal/_build/results?buildId=291917&view=logs&j=b48799ae-91e6-58f0-f267-33373aeec3a4&t=42dbf9bc-daa4-5984-64ee-478aaf0ec50d&s=d4729883-749f-5ec1-ddc8-190d167414cc - UsePythonVersion@0 task fails because network policies restrict pypi.org access when installing pip

(current) Example run: https://azfunc.visualstudio.com/internal/_build/results?buildId=292418&view=logs&jobId=35bc92f9-d4f9-539d-c334-5b5bd6a794ea&j=35bc92f9-d4f9-539d-c334-5b5bd6a794ea&t=19b8a4f6-5b46-5b60-2309-f02cc609a02d - installs pip through the internal feed.

Also includes minor pool updates for the release pipeline.

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)
  • runtimes/v1 / runtimes/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 (runtimes/v1)?
  • V2 programming model (runtimes/v2)?
• Explanation (if limited to one model):