Make kernel names unique in radix sort

[dmitriy-sobolev]

Fixes #1922. You can find elaborate description of the issue there.

It appears that _Proj, a lambda declared in __pattern_sort_by_key template, will have different types for different __patter_sort_by_key instantiations:
https://github.com/oneapi-src/oneDPL/blob/28cb633583570457a2e21a752f6a517f5fc7134a/include/oneapi/dpl/pstl/hetero/algorithm_impl_hetero.h#L1274-L1275

Here is a simplified example of a lambda having different types in different function template instantiations: https://godbolt.org/z/ddrM6Tseq

[adamfidel]

Makes sense to me. The projection operator should definitely be part of the kernel name since the lambda's type is embedding the input iterator, which can change for different calls.

[danhoeflinger]

LGTM