Pin compiler to minimum 2026.0.0

[ndgrigorian]

A number of new features in dpctl require newer compiler versions

This PR updates the minimum required DPC++ compiler version to 2026.0.0, as later versions should be compatible, but this sets a floor for where some features may be lost, and will allow the removal of some macros hiding features from later versions from earlier compilers

• 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?

[github-actions]

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

[coveralls]

coverage: 74.161% (+0.1%) from 74.023% — pin-compiler-minimum-to-2026 into master

[antonwolfy]

Thank you @ndgrigorian