Make the math module an extension package

In #81313 a new module math.integer was added. It was implemented as the _math_integer extension module, modified to look like a math submodule. This required assigning the integer attribute of the math module, setting sys.modules['math.integer'], patching the __name__ attribute of the new module and the __module__ attribute of its functions (to support help and pickling). Still, some implementation details are visible: sys.modules['_math_integer'], the __spec__ attribute of the new module. Also, it is difficult to stop importing the math.integer module automatically when the math module is imported.

Import machinery in principle supports extension packages and extension submodules, but there is no precedence of this in the stdlib, and it is not trivial to build them. The math module should be compiled into math/__init__.*.so instead of math.*.so, and math.integer correspondingly into math/integer.*.so. I believe this is possible.

Linked PRs

• gh-141363
• gh-144294
• gh-144339
• gh-152352

先阅读链接的 PR gh-141363、gh-144294、gh-144339 和 gh-152352，然后追踪 math 模块和 math.integer 扩展的构建与导入方式。预期结果是采用一种扩展包布局，避免暴露 _math_integer 和经过修补的元数据，并避免自动导入 math.integer。