Stack from ghstack:

• [FSDP] Rename unflat_param_name -> fqn for consistency #88123 [FSDP] Rename unflat_param_name -> fqn for consistency
• [FSDP] Simplify _get_buffer_names() #88122 [FSDP] Simplify _get_buffer_names()
• [FSDP] Remove unneeded torch.no_grad() context when offloading to CPU #88121 [FSDP] Remove unneeded torch.no_grad() context when offloading to CPU
• [FSDP][Docs] Add note mentioning rate limiter for backward prefetch #88120 [FSDP][Docs] Add note mentioning rate limiter for backward prefetch
• [FSDP()][27/N] Add forward hook registration #88040 [FSDP()][27/N] Add forward hook registration
• [FSDP()][26/N] Move _lazy_init() into _fsdp_root_pre_forward() #87941 [FSDP()][26/N] Move _lazy_init() into _fsdp_root_pre_forward()
• [FSDP()][25/N] Add _post_forward_reshard() #87940 [FSDP()][25/N] Add _post_forward_reshard()
• [FSDP()][24/N] Refactor _lazy_init() #87939 [FSDP()][24/N] Refactor _lazy_init()
• [FSDP()][23/N] Refactor handle attr initialization #87938 [FSDP()][23/N] Refactor handle attr initialization
• [FSDP] Simplify _reset_lazy_init() #87937 [FSDP] Simplify _reset_lazy_init()
• [FSDP()][22/N] Refactor _cast_buffers() in _lazy_init() #87936 [FSDP()][22/N] Refactor _cast_buffers() in _lazy_init()
• [FSDP()][21/N] Refactor and fix _cast_buffers() #87935 [FSDP()][21/N] Refactor _buffer_name_to_orig_dtype computation
• [FSDP] Rename dtype to buffer_name_to_dtype #87934 [FSDP] Rename dtype to buffer_name_to_dtype
• [FSDP] Remove device arg from _cast_buffers() #87933 [FSDP] Remove device arg from _cast_buffers()
• [FSDP()][20/N][Easy] Move functions in file #87932 [FSDP()][20/N][Easy] Move functions in file
• [FSDP()][18/N] Refactor pre_forward_unshard() #87931 [FSDP()][18/N] Refactor pre_forward_unshard()
• [FSDP()][17/N] Refactor _fsdp_root_pre_forward() #87930 [FSDP()][17/N] Refactor _fsdp_root_pre_forward()
• [FSDP()][16/N] Refactor post-forward/pre-backward #87929 [FSDP()][16/N] Refactor post-forward/pre-backward
• [FSDP()][15/N] Refactor _init_streams() #87928 [FSDP()][15/N] Refactor _init_streams()
• [FSDP()][14/N] Refactor pre-forward/post-backward #87927 [FSDP()][14/N] Refactor pre-forward/post-backward
• [FSDP()][13/N] Refactor unshard/reshard/grads #87926 [FSDP()][13/N] Refactor unshard/reshard/grads
• [FSDP()][12/N] Easy cleanup #87925 [FSDP()][12/N] Easy cleanup
• [FSDP()][10/N][11/N] Introduce composable (ctor only) #87924 [FSDP()][10/N][11/N] Introduce composable (ctor only)
• [FSDP()][9/N] Refactor ctor (continued) #87923 [FSDP()][9/N] Refactor ctor (continued)