Enable fx_graph_cache in gpt-fast example

[mreso]

Description

This PR enables fxGraphCache in the gpt-fast example to speed up compile time.

Fixes #(issue)

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Feature/Issue validation/testing

Please describe the Unit or Integration tests that you ran to verify your changes and relevant result summary. Provide instructions so it can be reproduced.
Please also list any relevant details for your test configuration.

• [X]pytest test/pytest/test_example_gpt_fast.py -k test_handler

===================================================================================================================== test session starts =====================================================================================================================
platform linux -- Python 3.10.12, pytest-7.3.1, pluggy-1.3.0
rootdir: /home/ubuntu/serve
plugins: mock-3.10.0, cov-4.1.0
collected 5 items / 3 deselected / 2 selected

test/pytest/test_example_gpt_fast.py ..                                                                                                                                                                                                                 [100%]

====================================================================================================================== warnings summary =======================================================================================================================
test/pytest/test_example_gpt_fast.py::test_handler[false]
  /home/ubuntu/serve/ts/torch_handler/base_handler.py:13: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
    from pkg_resources import packaging

test/pytest/test_example_gpt_fast.py::test_handler[false]
test/pytest/test_example_gpt_fast.py::test_handler[false]
  /home/ubuntu/miniconda3/envs/serve/lib/python3.10/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('zope')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
    declare_namespace(pkg)

test/pytest/test_example_gpt_fast.py::test_handler[false]
test/pytest/test_example_gpt_fast.py::test_handler[true]
test/pytest/test_example_gpt_fast.py::test_handler[true]
test/pytest/test_example_gpt_fast.py::test_handler[true]
  /home/ubuntu/miniconda3/envs/serve/lib/python3.10/site-packages/torch/backends/cuda/__init__.py:321: FutureWarning: torch.backends.cuda.sdp_kernel() is deprecated. In the future, this context manager will be removed. Please see, torch.nn.attention.sdpa_
kernel() for the new context manager, with updated signature.
    warnings.warn(

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
=================================================================================================== 2 passed, 3 deselected, 7 warnings in 79.21s (0:01:19) ====================================================================================================

• pytest test/pytest/test_example_gpt_fast.py -k test_gpt_fast_mar[mar_file_path0]

===================================================================================================================== test session starts =====================================================================================================================
platform linux -- Python 3.10.12, pytest-7.3.1, pluggy-1.3.0
rootdir: /home/ubuntu/serve
plugins: mock-3.10.0, cov-4.1.0
collected 5 items / 4 deselected / 1 selected

test/pytest/test_example_gpt_fast.py 2024-02-09T20:28:14,022 [INFO ] W-29500-gpt_fast_handler_1.0 TS_METRICS - ts_inference_latency_microseconds.Microseconds:6.3719938016E7|#model_name:gpt_fast_handler,model_version:default|#hostname:ip-172-31-15-101,time
stamp:1707510494
2024-02-09T20:28:14,022 [INFO ] W-29500-gpt_fast_handler_1.0 TS_METRICS - ts_queue_latency_microseconds.Microseconds:144.753|#model_name:gpt_fast_handler,model_version:default|#hostname:ip-172-31-15-101,timestamp:1707510494
2024-02-09T20:28:14,022 [INFO ] W-29500-gpt_fast_handler_1.0-stdout MODEL_METRICS - HandlerTime.ms:63717.68|#ModelName:gpt_fast_handler,Level:Model|#hostname:ip-172-31-15-101,requestID:69282a5f-3532-497e-863f-4824e81e505a,timestamp:1707510494
.                                                                                                                                                                                                                  [100%]

========================================================================================================= 1 passed, 4 deselected in 75.21s (0:01:15) ==========================================================================================================

Checklist:

• Did you have fun?
• Have you added tests that prove your fix is effective or that this feature works?
• Has code been commented, particularly in hard-to-understand areas?
• Have you made corresponding changes to the documentation?

[agunapal]

LGTM to me.
Can you please add a section in the README highlighting this example working with multiple GPUs.
The README talks about it with TP, but its not very obvious.