remove depency on --expt-relaxed-constexpr

[cwsmith]

The copy constructor of the KokkosController is being invoked and results in the following compiler warning. With commit 8debc89 --expt-relaxed-constexpr is being passed as a compiler option when the Kokkos CUDA backend is enable.

Ideally, I'd like to remove this as it may not be portable and is a 'experimental' feature. Note, Kokkos does not enable it by default for the latter reason.

    meshFields/src/MeshField_Shape.hpp(69): warning #20013-D:
    calling a constexpr __host__ function("
    
    Controller::KokkosController< ::Kokkos::CudaSpace,  ::Kokkos::Cuda, double *** > ::KokkosController(const Controller::KokkosController< ::Kokkos::CudaSpace,  ::Kokkos::Cuda, double *** > &)
    
    ") from a __host__ __device__ function("
    
    MeshField::MeshField< ::Controller::KokkosController< ::Kokkos::CudaSpace,  ::Kokkos::Cuda, double *** > > ::MeshField
    
    ") is not allowed. The experimental flag '--expt-relaxed-constexpr' can be used to allow this.
    
    Remark: The warnings can be suppressed with "-diag-suppress <warning-number>"

    meshFields/src/MeshField_Element.hpp(68): warning #20013-D:
    calling a constexpr __host__ function("
    
    Controller::KokkosController< ::Kokkos::CudaSpace,  ::Kokkos::Cuda, double ***, double *** > ::KokkosController(const Controller::KokkosController< ::Kokkos::CudaSpace,  ::Kokkos::Cuda, double ***, double *** > &)
    
    ") from a __host__ __device__ function("
    
    MeshField::MeshField< ::Controller::KokkosController< ::Kokkos::CudaSpace,  ::Kokkos::Cuda, double ***, double *** > > ::MeshField
    
    ") is not allowed. The experimental flag '--expt-relaxed-constexpr' can be used to allow this.