[booster] added the plugin base and torch ddp plugin

[FrankLeeeee]

📌 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

Fixed #3179

📝 What does this PR do?

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

This PR added the plugin base class and implemented a Torch DDP plugin as an exmaple

💥 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 87%.

Click me to view the complete report

Name                                                         Stmts   Miss  Cover
--------------------------------------------------------------------------------
colossalai/booster/booster.py                                   49     14    71%
colossalai/booster/plugin/__init__.py                            3      0   100%
colossalai/booster/plugin/plugin_base.py                        32      6    81%
colossalai/booster/plugin/torch_ddp_plugin.py                   45      9    80%
tests/test_booster/test_accelerator.py                          19      0   100%
tests/test_booster/test_mixed_precision/test_fp16_torch.py      35      1    97%
tests/test_booster/test_plugin/test_torch_ddp_plugin.py         55      0   100%
--------------------------------------------------------------------------------
TOTAL                                                          238     30    87%