Deprecate `cub::DeviceSpmv`

[gevtushenko]

The cub::DeviceSpmv was unmaintained for a while and probably contains bugs. Moreover, there are better implementations in specialized libraries like cuSPARSE. I suggest we deprecate it.

[bernhardmgruber]

@fbusato compared CUB to cuSPARSE and also reached the conclusion to deprecate the CUB implementation. See #3070
.