Backend: reevaluate minimum CPython target

Currently, the C extensions are built targeting Python 3.7. Most of our dependencies do not support it (Python 3.7) at all, but our extensions are fully compatible with the latest CPython releases.

Is there any benefit, especially performance-wise, if we raise the minimum to CPython 3.11, mirroring NumPy's policy?

No files or tests are named. Start by locating the C-extension build configuration and checking the supported Python versions of the dependencies, then compare builds targeting CPython 3.7 and 3.11 for compatibility and performance. Done means the project has a documented decision and, if the target changes, the build and support policy are updated consistently.

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