Speed up inspect.signature() for Python functions

inspect.signature() builds a Signature whose every Parameter is constructed through the public Parameter constructor, which validates the name and kind on each call. When the parameters come from a function's own code object the names are already valid identifiers and the kinds are already the canonical constants, so that validation re-checks facts that are guaranteed to hold.

Signature introspection runs constantly in the ecosystem: web frameworks resolving view and dependency arguments, CLI libraries like click, pytest fixture wiring, and serialization and validation layers all call it per function, often at import time while wiring an application together.

Taking the signature of 400 real callables collected from popular packages (requests, click, jinja2, sqlalchemy, werkzeug, flask and others) takes 1.46 ms today and 1.16 ms when trusted-source parameters skip the redundant validation, 26% faster, with the public Parameter() constructor and its validation unchanged for every other caller.

Linked PRs

• gh-150823
• gh-157463

首先跟踪 inspect.signature() 经过 Signature 和公共 Parameter 构造函数的调用流程，重点关注从函数代码对象获取的参数。将现有路径和 Trusted-Source 路径与 issue 中描述的 400-callable 基准进行比较，并验证公共 Parameter() 的验证保持不变，同时复现报告的性能改进。