Remove duplicate kernel instantiations across `libcuvs`

The rule of thumb is that any-time a kernel is launched from a TU (directly or indirectly) using the triple chevron syntax kernel<<<...>>>, a copy of the kernel will be included in that TU. This starts becoming a problem when the library has the same kernel instance being launched from multiple TUs.

The only solution is to make sure that the kernel is launched as part of a pre-compiled function, and other functions that need to launch the kernel only have visibility of the declaration of that pre-compiled function.

There are two ways to do this:

1. Call the function from the public API wherever possible
2. Create an internal shared header in src with only the declaration and defer the definition in a self-contained TU

Inspect libcuvs kernel launches under src and identify kernels instantiated from multiple translation units. Use public APIs where possible or add internal shared declarations with self-contained definitions, then verify that duplicate kernel instantiations are removed.