Use work-around for Coverage workflow

[ndgrigorian]

Coverage currently segfaults due to segfault when building with oneAPI 2026.0

As a work-around, use 2025.3 until the issue is resolved. Slips in a change bumping coverage workflow to Python 3.14 and making --cmake-opts actually work in gen_coverage and gen_docs scripts, an issue which was observed during reproduction of the crash.

• Have you provided a meaningful PR description?
• 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?

[coveralls]

Coverage is 75.476% — fix-coverage-workflow into master. No base build found for master.

[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/2300/index.html