Add module-swap UX for INT8 mixed-precision training #4852

Job	Run time
test (CPU 2.3, linux.4xlarge, torch==2.3.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job	7m 57s
test (CPU Nightly, linux.4xlarge, --pre torch --index-url https://download.pytorch.org/whl/nightl... / linux-job	10m 47s
test (CPU 2.5, linux.4xlarge, torch==2.5.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job	10m 47s
test (CPU 2.4, linux.4xlarge, torch==2.4.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job	8m 53s
test (CUDA 2.3, linux.g5.12xlarge.nvidia.gpu, torch==2.3.0, cuda, 12.1) / linux-job	27m 42s
test (CUDA 2.4, linux.g5.12xlarge.nvidia.gpu, torch==2.4.0, cuda, 12.1) / linux-job	38m 18s
test (CUDA Nightly, linux.g5.12xlarge.nvidia.gpu, --pre torch --index-url https://download.pytorc... / linux-job	1h 6m 46s
test (CUDA 2.5, linux.g5.12xlarge.nvidia.gpu, torch==2.5.0 --index-url https://download.pytorch.o... / linux-job	1h 1m 26s
	3h 52m 36s

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