Give tests and examples separate ruff configs (#158)

This allows more fine-grained lint rule adjustments, and allows
the examples to treat fastapi_cache as a 'third party' module, just
like users of the library would use it.

examples/in_memory/main.py

@@ -4,13 +4,12 @@ from typing import Dict, Optional
 import pendulum
 import uvicorn
 from fastapi import FastAPI
-from pydantic import BaseModel
-from starlette.requests import Request
-from starlette.responses import JSONResponse, Response
-
 from fastapi_cache import FastAPICache
 from fastapi_cache.backends.inmemory import InMemoryBackend
 from fastapi_cache.decorator import cache
+from pydantic import BaseModel
+from starlette.requests import Request
+from starlette.responses import JSONResponse, Response
 
 app = FastAPI()