[Draft][develop] Upgrade connexion to 2.15.0rc3, upgrade Werkzeug to 3.1.3 to address CVE

[hehe7318]

Description of changes

• Upgrade connexion to 2.15.0rc3(Temporary).
• Upgrade Werkzeug to ~=3.0.0 to address CVE.
• Upgrade serverless_wsgi.py to the latest version.
• Changes to encoder.py, flask_app.py and etc. to adapt the version bump.

Tests

• Changes to tests to adapt the version bump.
• Unit tests all passed.
• Integ tests on-going.

References

• Link to impacted open issues.
• Link to related PRs in other packages (i.e. cookbook, node).
• Link to documentation useful to understand the changes.

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

Please review the guidelines for contributing and Pull Request Instructions.

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