Unitxt 1.15.9

Main changes

• Artifacts in the catalog can now be links to other artifacts and can also be marked deprecated.

What's Changed

• artifact link by @dafnapension in #1363
• Add processors also as operators by @antonpibm in #1397
• added 'add_link_to_catalog' for easily adding artifact_links with/without deprecation msg by @dafnapension in #1398
• Safety updates by @bnayahu in #1391
• Reduce error message clutter by @yoavkatz in #1401
• Update version to 1.15.9 by @yoavkatz in #1404

Full Changelog: 1.15.8...1.15.9