Add docs for eager mode #9376

Job	Run time
get-torch-commit	3s
Build XLA CUDA plugin / build	5m 7s
Build PyTorch with CUDA / build	24m 10s
Build PyTorch/XLA / build	23m 18s
TPU tests	0s
GPU tests requiring torch CUDA / test (python_tests, linux.8xlarge.nvidia.gpu)	9m 56s
GPU tests requiring torch CUDA / test (triton_tests, linux.g5.4xlarge.nvidia.gpu)	5m 52s
Build docs / build-docs	1m 27s
GPU tests / test (benchmark_tests)	13m 19s
GPU tests / test (python_tests, xla_op1)	35m 3s
CPU tests / test (benchmark_tests)	8m 6s
GPU tests / test (python_tests, xla_op2)	8m 3s
CPU tests / test (python_tests, xla_op1)	12m 15s
GPU tests / test (python_tests, xla_op3)	43m 56s
CPU tests / test (python_tests, xla_op2)	3m 41s
GPU tests / test (python_tests, torch_mp_op)	52m 13s
CPU tests / test (python_tests, xla_op3)	5m 52s
GPU tests / test (cpp_tests, cpp_tests1)	9m 48s
CPU tests / test (python_tests, torch_mp_op)	16m 13s
GPU tests / test (cpp_tests, cpp_tests2)	16m 59s
CPU tests / test (cpp_tests, cpp_tests1)	4m 32s
CPU tests / test (cpp_tests, cpp_tests2)	4m 28s
	5h 4m 21s

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