[MAINT] Use SHA to pin GitHub actions

[ndgrigorian]

Public CI workflows have been using SHA and version pins interchangeably/at random, as workflows were added and updated sporadically, and this has become a mess

This PR addresses the technical debt by moving to SHA in all cases

Supersedes #2254

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• Have you added a test, reproducer or referred to an issue with a reproducer?
• Have you tested your changes locally for CPU and GPU devices?
• Have you made sure that new changes do not introduce compiler warnings?
• Have you checked performance impact of proposed changes?
• Have you added documentation for your changes, if necessary?
• Have you added your changes to the changelog?
• If this PR is a work in progress, are you opening the PR as a draft?

[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/2255/index.html

[github-actions]

Array API standard conformance tests for dpctl=0.22.0dev1=py310h93fe807_12 ran successfully.
Passed: 1244
Failed: 44
Skipped: 89