[bf16] add bf16 support for fused adam

[ver217]

📌 Checklist before creating the PR

• I have created an issue for this PR for traceability
• The title follows the standard format: [doc/gemini/tensor/...]: A concise description
• I have added relevant tags if possible for us to better distinguish different PRs

🚨 Issue number

Link this PR to your issue with words like fixed to automatically close the linked issue upon merge

e.g. fixed #1234, closed #1234, resolved #1234

#3839

📝 What does this PR do?

Summarize your work here.
if you have any plots/diagrams/screenshots/tables, please attach them here.

1. Add bf16 support for fused adam optimizer.
2. Update related tests.

💥 Checklist before requesting a review

• I have linked my PR to an issue (instruction)
• My issue clearly describes the problem/feature/proposal, with diagrams/charts/table/code if possible
• I have performed a self-review of my code
• I have added thorough tests.
• I have added docstrings for all the functions/methods I implemented

⭐️ Do you enjoy contributing to Colossal-AI?

• 🌝 Yes, I do.
• 🌚 No, I don't.

Tell us more if you don't enjoy contributing to Colossal-AI.

[github-actions]

The code coverage for the changed files is 91%.

Click me to view the complete report

Name                                             Stmts   Miss  Cover
--------------------------------------------------------------------
colossalai/nn/optimizer/fused_adam.py               55     10    82%
tests/test_optimizer/test_fused_adam.py             54      1    98%
tests/test_optimizer/test_fused_adam_kernel.py      46      3    93%
--------------------------------------------------------------------
TOTAL                                              155     14    91%