Python: use run_tasks_in_packages_if_exists script for all-tests

[ekzhu]

Motivation and Context

So we can properly skip tests in lab and devui in the main CI build

Description

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull Request Overview

This PR modifies the Python test execution to use a consistent script-based approach for running tests across packages while properly handling package exclusions. The main goal is to enable proper skipping of tests in lab and devui packages in the CI build.

• Replaced direct pytest command with script-based approach using run_tasks_in_packages_if_exists.py
• Added command-line argument parsing to support dynamic package exclusions
• Consolidated test execution methods by removing the separate all-tests-cov task

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
python/run_tasks_in_packages_if_exists.py	Enhanced script with argparse support and exclude functionality for flexible package filtering
python/pyproject.toml	Simplified test tasks by replacing direct pytest commands with script-based approach
.github/workflows/python-test-coverage.yml	Updated CI to use unified test command instead of separate coverage task

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[eavanvalkenburg]

This is much slower because it will have to setup and breakdown for each package