text: Title: `allow_x00=False` not affecting Headers and Cookies [BUG]
  Body: ### Checklist
  
  - [x] I checked the [FAQ section](https://schemathesis.readthedocs.io/en/stable/faq.html#frequently-asked-questions) of the documentation
  - [x] I looked for similar issues in the [issue tracker](https://github.com/schemathesis/schemathesis/issues)
  - [x] I am using the latest version of Schemathesis
  
  ### Describe the bug
  
  When running Schemathesis tests, I get errors from Postgres about null bytes. Possibly related to #2072.
  
  ### To Reproduce
  
  1. Install FastAPI and Schemathesis.
  
  2. Run this code:
  ```python
  import warnings
  from typing import Annotated
  
  import schemathesis
  from fastapi import Cookie, FastAPI, Header
  from hypothesis.errors import NonInteractiveExampleWarning
  from schemathesis.generation import GenerationConfig
  
  warnings.filterwarnings("ignore", category=NonInteractiveExampleWarning)
  
  app = FastAPI()
  
  
  @app.post("/test")
  def test(x_test: Annotated[str, Header()], test_cookie: Annotated[str, Cookie()]):
      return x_test
  
  
  schemathesis.experimental.OPEN_API_3_1.enable()
  schema = schemathesis.from_asgi(
      "/openapi.json",
      app,
      generation_config=GenerationConfig(allow_x00=False),
  )
  
  operation = schema["/test"]["POST"]
  strategy = operation.as_strategy()
  
  
  while True:
      case = strategy.example()
      if "\x00" in case.headers["x-test"]:
          print("Found null byte in header")
          break
  
  while True:
      case = strategy.example()
      if "\x00" in case.cookies["test_cookie"]:
          print("Found null byte in cookie")
          break
  ```
  3. After a few seconds, it should print that it found null bytes.
  
  I also checked query parameters and form data, but those seemed to respect the configuration option.
  
  Please include a minimal API schema causing this issue:
  The API schema from the code above:
  ```json
  {'openapi': '3.1.0', 'info': {'title': 'FastAPI', 'version': '0.1.0'}, 'paths': {'/test': {'post': {'summary': 'Test', 'operationId': 'test_test_post', 'parameters': [{'name': 'x-test', 'in': 'header', 'required': True, 'schema': {'type': 'string', 'title': 'X-Test'}}, {'name': 'test_cookie', 'in': 'cookie', 'required': True, 'schema': {'type': 'string', 'title': 'Test Cookie'}}], 'responses': {'200': {'description': 'Successful Response', 'content': {'application/json': {'schema': {}}}}, '422': {'description': 'Validation Error', 'content': {'application/json': {'schema': {'$ref': '#/components/schemas/HTTPValidationError'}}}}}}}}, 'components': {'schemas': {'HTTPValidationError': {'properties': {'detail': {'items': {'$ref': '#/components/schemas/ValidationError'}, 'type': 'array', 'title': 'Detail'}}, 'type': 'object', 'title': 'HTTPValidationError'}, 'ValidationError': {'properties': {'loc': {'items': {'anyOf': [{'type': 'string'}, {'type': 'integer'}]}, 'type': 'array', 'title': 'Location'}, 'msg': {'type': 'string', 'title': 'Message'}, 'type': {'type': 'string', 'title': 'Error Type'}}, 'type': 'object', 'required': ['loc', 'msg', 'type'], 'title': 'ValidationError'}}}}
  ```
  
  ### Expected behavior
  
  Using the `allow_x00` configuration option should prevent null bytes in all strings.
  
  ### Environment
  
  ```
  - OS: Linux
  - Python version: 3.12
  - Schemathesis version: 3.28.1
  - Spec version: Open API 3.1.0
  ```