[HLSL] Reintroduce dx.disable_optimizations to set DisableOptimization Shader Flag (#180069)
This patch removes optnone from HLSL entry functions and instead uses
`dx.disable_optimizations` module flag to know when to enable
`DisableOptimization` Shader Flag. This is part of: #167936
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Co-authored-by: Joao Saffran <jderezende@microsoft.com>