[Misc] Heterogeneous GPU Optimizer Logging Clean Up

[nwangfw]

Pull Request Description

In this PR, we clean up the GPU optimizer's logging information.

(1) using snake case format
(2) Removed uvicorn.error, which is confusing
(3) modified the default GPU cost from 0 to inf, In this case, the OPU optimizer will never use a GPU type without profiling.

Related Issues

Resolves: #502

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[Jeffwan]

excellent! this helps a lot in our observation

[Jeffwan]

this looks good to me