Add smtp_port support to settings module

[mangopep]

Description

Adds support for configuring smtp_port in the dellemc.powerscale.settings module. The change adds the new module parameter, includes it in the email settings update payload, and updates documentation, sample playbook, mocks, and unit tests.

GitHub Issue #
Fixes #257

Checklist:

• I have performed a self-review of my own code to ensure there are no formatting, pep8, linting, or security issues
• I have performed Ansible Sanity test using --docker default
• I have verified that new and existing unit tests pass locally with my changes
• I have not allowed coverage numbers to degenerate
• I have maintained at least 90% code coverage
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• Backward compatibility is not broken

How Has This Been Tested?

• Ran targeted unit tests for the settings module:

  ANSIBLE_COLLECTIONS_PATH=/private/tmp PYTHONPATH=/private/tmp \
  /Users/Desktop/ansible-powerscale/.venv/bin/python -m pytest \
  tests/unit/plugins/modules/test_settings.py -v