Kernel build

[reyna-abhyankar]

Description of changes:

Build all operator .cu files in lib/kernels

Note: there is an issue with embedding.cu with the half datatype. All other operators are building.

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This change is 

[lockshaw]

@reyna-abhyankar Can you add the cuda part of kernels to CI as part of this PR? Otherwise it'll just break immediately

[lockshaw]

lib/op-attrs/include/op-attrs/activation.h line 8 at r1 (raw file):

namespace FlexFlow {

enum class Activation { RELU, SIGMOID, TANH, GELU, NONE };

Why not just use std::optional<Activation> where you need this behavior?

[lockshaw]

@reyna-abhyankar Ignore the above, it was already added.