[Cleanup] Delete FSDP1 code

[ebsmothers]

A number of our APIs are holdovers from FSDP1 and can be deleted. A (probably non-exhaustive) list:

• FSDPPolicyType
• contains_fsdp
• dummy_reset_params
• prepare_model_for_fsdp_with_meta_device
• lora_fsdp_wrap_policy
• get_full_finetune_fsdp_wrap_policy
• memory_efficient_wrap_policy
• validate_state_dict_for_lora: this one is slightly different, but was only added due to some funny business about FSDP state dict key modifications. It's still used here, but that should be moved to validate_missing_and_unexpected_for_lora.

Apart from the last one, the only usage of all these APIs should be in unit tests. When deleting the test cases, we should also make sure that we have corresponding test cases for any analogous FSDP2 APIs.