Feature or enhancement

@itamaro is working on setting up additional buildbots for PEP 703 builds. To support this, we'll add an optional --disable-gil flag to the configure. For now, this flag won't do anything other than define the Py_NOGIL macro, but once the buildbots are setup, any future code behind this flag will be tested in the CI.

Linked PRs

• gh-108223: Add --disable-gil to configure #108227
• gh-108223: Document --disable-gil flag in configure #108236
• gh-108223: test.pythoninfo and libregrtest log Py_NOGIL #108238
• gh-108223: Add [NOGIL] marker to sys.version #108239
• gh-111062: Add nogil build test on GitHub Actions #111060
• gh-108223: Refer to PEP 703 as Free Threading #112780