✨ Add support for not needing ... as default value in required Query(), Path(), Header(), etc. (#4906)

* ✨ Do not require default value in Query(), Path(), Header(), etc

* 📝 Update source examples for docs with default and required values

* ✅ Update tests with new default values and not required Ellipsis

* 📝 Update docs for Query params and update info about default value, required, Ellipsis

docs_src/cookie_params/tutorial001.py

@@ -1,4 +1,4 @@
-from typing import Optional
+from typing import Union
 
 from fastapi import Cookie, FastAPI
 
@@ -6,5 +6,5 @@ app = FastAPI()
 
 
 @app.get("/items/")
-async def read_items(ads_id: Optional[str] = Cookie(None)):
+async def read_items(ads_id: Union[str, None] = Cookie(default=None)):
     return {"ads_id": ads_id}