move cached strings to global objects

[ericsnowcurrently]

There are ~80 str objects that get manually cached in CPython's core code. Each of these should be moved to _PyRuntimeState.

https://bugs.python.org/issue46765

[gvanrossum]

By "cached" do you mean interned? Or something else?

[ericsnowcurrently]

They have a static variable that will hold the object and then create/set it if NULL.

[ericsnowcurrently]

python/cpython#31366