Change: Migrate release changelog generation from Pontos to git-cliff

[easamoah7]

What:
Replaced Pontos-based changelog generation with git-cliff in release workflows.

Why:
To standardize and automate changelog generation, and remove the Pontos dependency.

How:

• Updated release workflows to use git-cliff.
• Removed Pontos references and config files.
• Verified changelog output and workflow execution.

Checklist:

• Pontos removed
• git-cliff added & tested
• Docs updated

JIRA: DOS-371