Use `sys.monitoring` once coverage.py supports it

[benoit74]

In 036a5ec, we've made configuration changes to ensure coverage still works with Cython 3.1

The issue is that:

• coverage has switched to sys.monitoring core to collect profile / linetracing in 7.9.1 on Python 3.14+: https://coverage.readthedocs.io/en/latest/changes.html#version-7-9-1-2025-06-13
• Cython also uses sys.monitoring profile / linetracing by default since 3.1 (see Implement PEP-669 sys.monitoring support cython/cython#6144)

The commit referenced above hence asked:

• coverage to use the ctrace core
• Cython to not use sys.monitoring for profile / linetracing

This needs to be rolled-back (to use sys.monitoring which is expected to be way more performant) once coverage supports plugins with sys.monitoring (probably coveragepy/coveragepy#1790 is the issue to follow).