Native context reinterpret casted as `pi_context`

[hdelan]

https://github.com/oneapi-src/oneMKL/blob/develop/src/blas/backends/cublas/cublas_scope_handle.cpp#L90
https://github.com/oneapi-src/oneMKL/blob/develop/src/blas/backends/rocblas/rocblas_scope_handle.cpp#L106

This is very bad. This has previously worked since the pi_context ie ur_context_handle_t had a native context (ie hipCtx_t) as its first member. But this is no longer the case in HIP adapter since oneapi-src/unified-runtime#999 .

Can someone please explain the intent of this code? I don't understand why pi_contexts are being used at all. They are not the same as native contexts.

Other changes are needed to accommodate the multi dev ctx switch. ie it is no longer correct to call get_native for a SYCL context, and will lead to undesirable behaviour on a multi GPU system. I can make these changes once the intent of this code is clarified a bit.