SyclPlatform equality testing and hashing implemented

[oleksandr-pavlyk]

While testing dpctl in the flat device hierarchy mode I realized we have not implemented equality testing for dpctl.SyclPlatform which caused test test_sycl_context.py::test_multi_device_different_platforms to fail.

This PR implements DPCTLPlatform_AreEq, DPCTLPlatform_Hash, adds tests and implaments dpctl.SyclPlatform.__equal__ and dpctl.SyclPlatform.__hash__ based on these.

Incidentally this PR also corrects declaration of DPCTLContext_Hash which mistakenly used __dpctl_take instead of __dpctl_keep annotation.

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[coveralls]

coverage: 84.953% (+0.03%) from 84.923% when pulling e54aaa0 on sycl-platform-equal into b055ff9 on master.

[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/1333/index.html

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev1=py310h7bf5fec_37 ran successfully.
Passed: 913
Failed: 87
Skipped: 119

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev1=py310h7bf5fec_37 ran successfully.
Passed: 913
Failed: 87
Skipped: 119

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev1=py310h7bf5fec_38 ran successfully.
Passed: 913
Failed: 87
Skipped: 119

[github-actions]

Deleted rendered PR docs from intelpython.github.com/dpctl, latest should be updated shortly. 🤞

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev1=py310h7bf5fec_40 ran successfully.
Passed: 913
Failed: 87
Skipped: 119