Accept a function (`module_name:function_name`) in `-X presite` and `PYTHON_PRESITE`

[vstinner]

Currently, it's only possible to specify a module name when using -X presite command line option and PYTHON_PRESITE environment variable: module imported before the site module is imported.

I propose extending the format to accept an entry point format: module_name:function_name; see pkgutil.resolve_name().

Note: the presite option is only available when Python is built in debug mode.

Linked PRs

• gh-148014: Accept a function name in -X presite option #148015