✨ 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/query_params_str_validations/tutorial005.py

@@ -4,7 +4,7 @@ app = FastAPI()
 
 
 @app.get("/items/")
-async def read_items(q: str = Query("fixedquery", min_length=3)):
+async def read_items(q: str = Query(default="fixedquery", min_length=3)):
     results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
     if q:
         results.update({"q": q})