[BUG]: unify _CCCL_FORCEINLINE and _CCCL_ALWAYS_INLINE

[ericniebler]

Is this a duplicate?

• I confirmed there appear to be no duplicate issues for this bug and that I agree to the Code of Conduct

Type of Bug

Something else

Component

libcu++

Describe the bug

cccl has _CCCL_FORCEINLINE and _CCCL_ALWAYS_INLINE. there should be only one. also, _CCCL_FORCEINLINE currently expands to inline when not using a CUDA compiler. that is unexpected. it should expand to either __attribute__((always_inline)) or __forceinline depending on which is supported by the host compiler.

How to Reproduce

n/a

Expected behavior

n/a

Reproduction link

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Operating System

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nvidia-smi output

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NVCC version

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