Drop support for Python 3.9

[ndgrigorian]

This PR proposes dropping Python 3.9 support from the project

NumPy and most of the ecosystem has already done the same for some time

includes a bump to find_package(Python 3.9...) to 3.10 in dpctl-config.cmake

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• Have you made sure that new changes do not introduce compiler warnings?
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[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=0.22.0dev0=py310h93fe807_2 ran successfully.
Passed: 1115
Failed: 6
Skipped: 119

[coveralls]

coverage: 86.005%. remained the same
when pulling cf3af4e on drop-python-3.9
into 2d0fd6b on master.

[antonwolfy]

Thank you @ndgrigorian, no more comments from me.