[Dependencies] Upgrade Python to version 3.14 (from 3.12) in all ParallelCluster lambda functions.

[gmarciani]

Description of changes

Upgrade Python to version 3.14 (from 3.12) in all ParallelCluster lambda functions.
Verified that python314 runtime is supported by Lambda also in US isolated regions.

As part of this update, we also:

1. upgraded Python to 3.14 for tests (gh workflows and 1-click templates used for testing)
2. upgraded fabric (test dependency) that was pinned to an old version due to a bug that has then been solved. the upgrade was a blocker to python 3.14.

Tests

• PR checks (they include the updates)
• [SUCCESS] integ test:

test-suites:
  basic:
    test_essential_features.py::test_essential_features:
      dimensions:
        - regions: ["us-east-1"]
          instances: ["c5.xlarge"]
          oss: ["alinux2023"]
          schedulers: ["slurm"]

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.08%. Comparing base (369130e) to head (95f761e).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7653      +/-   ##
===========================================
- Coverage    90.08%   90.08%   -0.01%     
===========================================
  Files          180      180              
  Lines        16413    16405       -8     
===========================================
- Hits         14786    14778       -8     
  Misses        1627     1627              

Flag	Coverage Δ
unittests	90.08% <ø> (-0.01%)	⬇️

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