Update HIP target handling using alias

[vlad-perevezentsev]

This PR suggests simplifying DPCTL_TARGET_HIP handling by using target aliases amd_gpu_<arch> and removing support for amdgcn-amd-amdhsa target.
Also updates docs to clarify how to determine and use the correct AMD GPU architecture.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/2099/index.html

[github-actions]

Array API standard conformance tests for dpctl=0.21.0dev0=py310h93fe807_22 ran successfully.
Passed: 1116
Failed: 5
Skipped: 119