Fix Python 3.14 test timeout: replace utcnow() and remove tee pipe

[RyAuld]

Problem

Python 3.14 unit tests intermittently stall at 99% completion, hitting the 5-minute step timeout. The last output before the hang is:

\
##[warning]datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version.
\\

Root Cause

Two issues contribute:

1. \datetime.utcnow()\ deprecation — emits a \DeprecationWarning\ on Python 3.12+ and is scheduled for removal in 3.14+
2. \2>&1 | tee\ pipe deadlock — after pytest finishes, the pipe to \ ee\ can hang waiting for file descriptors to close on Python 3.14

Fix

• Replace \datetime.utcnow()\ with \datetime.now(timezone.utc)\ in \msal/wstrust_request.py\ (compatible with Python 3.2+)
• Replace \2>&1 | tee test-results/pytest-unit.log\ with pytest's native --log-file\ option, eliminating the pipe entirely

Testing

• Local wstrust tests pass
• CI results from this PR will confirm the fix across all Python versions

[Copilot]

Pull request overview

This PR addresses intermittent CI timeouts on Python 3.14 by removing a deprecated datetime.utcnow() usage that emits warnings, and by eliminating a shell tee pipeline that can hang at the end of the unit test run.

Changes:

• Replace datetime.utcnow() with timezone-aware datetime.now(timezone.utc) in WS-Trust request timestamp generation.
• Update the unit-test Azure Pipelines step to use pytest’s --log-file instead of 2>&1 | tee, removing the pipe.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
msal/wstrust_request.py	Avoids deprecated utcnow() by generating UTC timestamps via datetime.now(timezone.utc).
.Pipelines/template-pipeline-stages.yml	Removes tee piping from the unit-test pytest invocation and writes logs via --log-file instead.

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