[Bugfix] Fix test fused quant layernorm tests

[ElizaWszola]

Fix optional vs. bool type issue in test_fused_quant_layernorm.py. This allows int8 tests to run correctly.

TODO: fix unit test failures

[yewentao256]

After we fix the scale_ub case in unit test, we now face three known issues.

• precision error for int8
• precision error for fp8
• illegal memory access without setting scale_ub

And I fix all of them in my commits

reserve core]$ pytest test_fused_quant_layernorm.py -x
============= test session starts ==============
platform linux -- Python 3.12.11, pytest-8.4.2, pluggy-1.6.0
rootdir: /home/yewentao256/vllm-source
configfile: pyproject.toml
plugins: anyio-4.11.0
collected 576 items                            

test_fused_quant_layernorm.py .......... [  1%]
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......                                   [100%]

= 576 passed, 2 warnings in 160.03s (0:02:40) ==