Patch release: Multi-tag instead of single tags for xxxTrainer

This is a patch release to push multiple tags (e.g. trl & sft) instead of one tag

What's Changed

• Release: v0.7.5 by @younesbelkada in #1131
• set dev version by @younesbelkada in #1132
• [xxxTrainer] multi-tags support for tagging by @younesbelkada in #1133

Full Changelog: v0.7.5...v0.7.6