Fix Params4bit attribute access for FSDP state_dict traversal #102

Job	Run time
CUDA (windows, T4, 11.8.0, 2.7.1, https://download.pytorch.org/whl/cu118) / build	3m 53s
CUDA (linux-x64, L40S, 11.8.0) / build	2m 41s
CUDA (linux-x64, L40S, 13.0.2) / build	3m 4s
CUDA (linux-x64, T4, 11.8.0) / build	2m 29s
CUDA (linux-x64, T4, 13.0.2) / build	2m 25s
CUDA (linux-x64, L40S, 12.8.1) / build	2m 57s
CPU (linux-aarch64, 2.9.1) / build	16s
CPU (linux-x64, 2.9.1) / build	19s
CPU (macos, 2.9.1) / build	17s
CUDA (linux-x64, T4, 12.8.1) / build	3m 5s
CPU (macos, 2.3.1) / build	19s
CPU (linux-x64, icelake, 2.3.1) / build	19s
CPU (linux-aarch64, 2.5.1) / build	14s
CPU (linux-x64, icelake, 2.9.1) / build	13s
CPU (linux-x64, 2.3.1) / build	16s
CPU (linux-x64, icelake, 2.9.1) / test	9m 2s
CPU (linux-x64, 2.3.1) / test	9m 30s
CPU (linux-aarch64, 2.5.1) / test	8m 38s
CPU (macos, 2.9.1) / test	12m 47s
CPU (linux-x64, 2.9.1) / test	15m 13s
CPU (linux-x64, icelake, 2.3.1) / test	8m 4s
CPU (linux-aarch64, 2.9.1) / test	10m 34s
CPU (macos, 2.3.1) / test	11m 52s
CUDA (linux-x64, T4, 13.0.2) / test	8m 42s
CUDA (linux-x64, T4, 11.8.0) / test	5m 59s
CUDA (linux-x64, L40S, 11.8.0) / test	3m 57s
CUDA (linux-x64, L40S, 12.8.1) / test	6m 50s
CUDA (linux-x64, L40S, 13.0.2) / test	6m 23s
CUDA (linux-x64, T4, 12.8.1) / test	10m 52s
CUDA (windows, T4, 11.8.0, 2.7.1, https://download.pytorch.org/whl/cu118) / test	16m 31s
	2h 47m 41s

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