Add package version option for python fastapi generator

[wing328]

based on #21609 with minor improvements, updated urlib3 to latest version

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
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Summary by cubic

Adds support for explicit package versioning in the Python FastAPI generator using packageVersion, now used in setup.cfg for generated servers. Updates samples to demonstrate the new field.

• New Features

  • The generator reads packageVersion and sets it as the package version in setup.cfg (independent from appVersion). Samples use 3.4.5.

• Dependencies

  • Bumped urllib3 from 2.6.3 to 2.7.0 in templates and samples.

^{Written for commit 582a604. Summary will update on new commits.}