fix(ci): update artifact actions to v4 for unit/integration coverage …

[Priyanshubhartistm]

Description

Updated actions/upload-artifact and actions/download-artifact to v4 in CI workflow. Added unique artifact names for each job.

Related Issue

Fixes #391

Motivation and Context

CI was failing due to deprecated artifact actions. This update restores artifact upload/download in all jobs and prevents future breakage.

How Has This Been Tested?

Ran workflow linting and all unit/integration tests locally. Verified artifact steps and coverage report handling.

Screenshots (if appropriate):

Types of changes

• Non-functional change (docs, style, minor refactor)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my code changes.
• All new and existing tests passed.