Removing the limitation of 256KB for header size

[gahfy]

This allows users to not be restricted to the limitation of 256KB for the size of the header, in order to solve #8472 :

How to reproduce

Python3 server code

import socket
import random
import string

def generate_random_string(length):
    return ''.join(random.choices(string.ascii_letters + string.digits, k=length))

random_string = ''.join(random.choices(string.ascii_letters + string.digits, k=256 * 1024 - 48))

# Création d'un socket TCP
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as server_socket:
    server_socket.bind(('127.0.0.1', 8080))
    server_socket.listen()

    while True:
        conn, addr = server_socket.accept()
        with conn:
            response = (
                "HTTP/1.1 200 OK\n"
                "Content-Type: text/plain\n"
                f"MyHeader:{random_string}\n"
                "Content-Length: 14\n"
                "\n"
                "Erreur de requête"
            )
            conn.sendall(response.encode('utf-8'))

Kotlin Client code after/before the PR (Comment/Uncomment lines 10/11)

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.ResponseBody;
import okhttp3.internal.http1.HeadersReader;

public class OkHttpTest {
  private static final String ENDPOINT = "http://127.0.0.1:8080";

  public static void main(String... args) {
    OkHttpClient client = new OkHttpClient.Builder().build();
    //OkHttpClient client = new OkHttpClient.Builder().headerSizeLimit(HeadersReader.HEADER_NO_LIMIT).build();

    try {
      Request request = new Request.Builder()
        .url(ENDPOINT)
        .build();
      try (Response response = client.newCall(request).execute()) {
        ResponseBody body = response.body();
        System.out.println(body.string());
      }
    } catch(Exception e) {
      e.printStackTrace();
    }
  }
}

Before, you will get an EOFException, after, everything works fine