Remove support for Python 3.7

[CasperWA]

Copilot summary

This pull request includes multiple changes to update the supported Python versions across various configuration files and scripts. The most important changes involve removing support for Python 3.7 and ensuring compatibility with Python 3.8 and higher.

Updates to supported Python versions:

• .github/workflows/_local_ci_tests.yml: Removed Python 3.7 from the matrix of supported Python versions. [1] [2]
• .github/workflows/cd_release.yml: Updated the validation logic to exclude Python 3.7 and updated the list of supported versions.
• .github/workflows/ci_cd_updated_default_branch.yml: Updated the validation logic to exclude Python 3.7 and updated the list of supported versions.
• .github/workflows/ci_check_pyproject_dependencies.yml: Updated the validation logic to exclude Python 3.7 and updated the list of supported versions.
• .github/workflows/ci_tests.yml: Updated the validation logic to exclude Python 3.7 and updated the list of supported versions.
• .pre-commit-config.yaml: Removed references to Python 3.7 and updated the pyupgrade hook to use --py38-plus. [1] [2]
• docs/workflows/ci_tests.md: Updated the example Python versions to exclude Python 3.7 and use Python 3.9 for documentation. [1] [2]
• pyproject.toml: Removed Python 3.7 from the classifiers and updated the requires-python field to ~=3.8. Updated dependencies and tools to be compatible with Python 3.8 and higher. [1] [2] [3] [4]
• tests/tasks/test_update_deps.py: Updated test cases to use Python 3.8 instead of Python 3.7. [1] [2] [3] [4] [5]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.61%. Comparing base (8ecd62c) to head (a83b20f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #315   +/-   ##
=======================================
  Coverage   84.61%   84.61%           
=======================================
  Files          12       12           
  Lines         936      936           
=======================================
  Hits          792      792           
  Misses        144      144           

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