[Draft] Update sparse API for cuSPARSE/rocSPARSE support

[Rbiessy]

Update the sparse API to more easily support other backends. This is a work in progress, only the API related to the data types and the trsv operation is updated. Only the trsv buffer test is compiling currently. Some TODOs are remaining.

Main take away so far are:

• The current API does not use templates for opaque pointer types. This makes supporting buffers difficult and adds a cost on the host side but makes the API closer to cuSPARSE.
• The API will change a bit more:
  • Non-compute functions should be synchronous (not return an event and not take dependencies)
  • buffer_size function should take a reference to an unsigned value
  • functions to reset matrix and vector data are missing
  • It's not clear whether we will need some kind of view type. cuSPARSE does not have an equivalent but it may be needed for MKL backends?