PEP 695 (Type Parameter Syntax) tracker - Generics

This issue is supposed to track when we can start to use the improved generics syntax introduced in Python 3.12 (PEP 695 in typeshed. Support is needed in released versions of:

• mypy
• pytype (optional)
• pyright
• PyCharm (optional)

As this is a syntax change, it's unlikely that we can add support before mypy drops support for running under Python 3.11 and below.

Example from the PEP:

class ClassA[T: str]:
    def method1(self) -> T:
        ...

def func[T](a: T, b: T) -> T:
    ...

从 PEP 695 开始，验证 mypy、pytype、pyright 和 PyCharm 的已发布版本支持状态。当相关工具支持 typeshed 中的语法，并且可以更新对应的 checklist 条目时，tracker 就完成了。