Model:Implement GraphGPT and LLaGA

[VoidHaruhi]

Description

Add implementation of GraphGPT and LLaGA model (some additional py files are added as common modules for Graph+LLM)

Checklist

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [$CATEGORY] (such as [NN], [Model], [Doc], [Feature]])
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented
• To the best of my knowledge, examples are either not affected by this change,
  or have been fixed to be compatible with this change
• Related issue is referred in this PR

Changes