Add separate e2e test for send_intermediate_prediction_response

[mreso]

Description

Add separate e2e test for send_intermediate_prediction_response
Additionally, it enables streaming in gpt-fast example test

Type of change

Please delete options that are not relevant.

• New test (non-breaking change which adds functionality)

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.

• pytest test/pytest/test_send_intermediate_prediction_response.py

======================================================================================= test session starts =======================================================================================
platform linux -- Python 3.10.13, pytest-7.3.1, pluggy-1.3.0
rootdir: /home/ubuntu/serve
plugins: mock-3.12.0, cov-4.1.0
collected 2 items

test/pytest/test_send_intermediate_prediction_response.py .2024-01-12T20:17:13,380 [INFO ] W-9000-tp_model_1.0 TS_METRICS - WorkerThreadTime.Milliseconds:3.0|#Level:Host|#hostname:ip-172-31-15-101,timestamp:1705090633
.                                                                                                                                [100%]

======================================================================================== 2 passed in 5.78s ========================================================================================

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?

[agunapal]

LGTM