[WIP] Use more compile time options in PushPX kernel

[lucafedeli88]

No description provided.

[AlexanderSinn]

Looks good! In HiPACE++ we use kernels with up to 48 compile-time variants, so I agree WarpX can use more. I would like to suggest two small changes:

• Use CompileTimeOptions<false, true> or  CompileTimeOptions<0, 1> instead of the enums. The compile time options use int internally, so the enums provide no extra type safety. To me, it looks like the enums add extra confusion, although this could be debatable.
• Use if instead ofif constexpr, but still with the ..._control check inside it. In my testing, this gives still all the performance benefits since compilers can easily optimize out if (false) {...} while avoiding the lambda campture issues that arise with NVCC.