* refactor low level zero
* fix zero2 and support cpu offload
* avg gradient and modify unit test
* refactor grad store, support layer drop
* refactor bucket store, support grad accumulation
* fix and update unit test of zero and ddp
* compatible with tp, ga and unit test
* fix memory leak and polish
* add zero layer drop unittest
* polish code
* fix import err in unit test
* support diffenert comm dtype, modify docstring style
* polish code
* test padding and fix
* fix unit test of low level zero
* fix pad recording in bucket store
* support some models
* polish
* [bf16] add bf16 support for fused adam (#3844)
* [bf16] fused adam kernel support bf16
* [test] update fused adam kernel test
* [test] update fused adam test
* [bf16] cpu adam and hybrid adam optimizers support bf16 (#3860)
* [bf16] implement mixed precision mixin and add bf16 support for low level zero (#3869)
* [bf16] add mixed precision mixin
* [bf16] low level zero optim support bf16
* [text] update low level zero test
* [text] fix low level zero grad acc test
* [bf16] add bf16 support for gemini (#3872)
* [bf16] gemini support bf16
* [test] update gemini bf16 test
* [doc] update gemini docstring
* [bf16] add bf16 support for plugins (#3877)
* [bf16] add bf16 support for legacy zero (#3879)
* [zero] init context support bf16
* [zero] legacy zero support bf16
* [test] add zero bf16 test
* [doc] add bf16 related docstring for legacy zero