Fixes https://github.com/pydantic/pydantic/issues/7611

Long term I think a plan to allow pydantic-core to minimize the validation runtime cost of using referenced schemas (https://github.com/pydantic/pydantic-core/pull/989) makes the most sense, but this will do for now. We may even be able to add back some of the caching, but will have to be smarter about it.

This degrades the performance of [this schema building benchmark](https://github.com/pydantic/pydantic/blob/main/tests/benchmarks/test_fastapi_startup_generics.py) from `2.5s` to `3s` on my laptop.

Selected Reviewer: @dmontagu
Remove schema building caches. Fixes https://github.com/pydantic/pydantic/issues/7611

Long term I think a plan to allow pydantic-core to minimize the validation runtime cost of using referenced schemas (https://github.com/pydantic/pydantic-core/pull/989) makes the most sense, but this will do for now. We may even be able to add back some of the caching, but will have to be smarter about it.

This degrades the performance of [this schema building benchmark](https://github.com/pydantic/pydantic/blob/main/tests/benchmarks/test_fastapi_startup_generics.py) from `2.5s` to `3s` on my laptop.

Selected Reviewer: @dmontagu
from __future__ import annotations as _annotations

from dataclasses import dataclass


@dataclass
class PydanticRecursiveRef:
    type_ref: str

    __name__ = 'PydanticRecursiveRef'
    __hash__ = object.__hash__

    def __call__(self) -> None:
        """Defining __call__ is necessary for the `typing` module to let you use an instance of
        this class as the result of resolving a standard ForwardRef.
        """

from __future__ import annotations as _annotations

from dataclasses import dataclass


@dataclass
class PydanticRecursiveRef:
    type_ref: str

    __name__ = 'PydanticRecursiveRef'
    __hash__ = object.__hash__

    def __call__(self) -> None:
        """Defining __call__ is necessary for the `typing` module to let you use an instance of
        this class as the result of resolving a standard ForwardRef.
        """
