Improve prevent-xhr — modify response

[AdamWr]

Basically the same issue as here - https://github.com/AdguardTeam/Scriptlets/issues/199#issuecomment-1063271758, but for response (currently only responseText is modified).

Steps to reproduce:

1. Add this rule:

   example.org#%#//scriptlet('prevent-xhr', 'pagead2.googlesyndication.com')

2. Go to - https://example.org/

3. Run this script:

   (() => {
   function reqListener() {
   if (this.status !== 200 || this.responseText === "" || this.response === "") {
     alert("adblock");
   } else {
     (() => {
       let video = '<iframe width="560" height="315" src="https://www.youtube.com/embed/Fy2rtb95QhY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>';
       let createDiv = document.createElement("div");
       document.body.appendChild(createDiv);
       createDiv.innerHTML = video;
     })();
   }
   }
   
   var oReq = new XMLHttpRequest();
   oReq.addEventListener("load", reqListener);
   oReq.open("GET", "https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js");
   oReq.send();
   })();

   Alert will be displayed, because this.response returns "". If pagead2.googlesyndication.com/pagead/js/adsbygoogle.js is not blocked then video player is loaded.

In this line: https://github.com/AdguardTeam/Scriptlets/blob/804c53527008e62ffcd296e3f36543c472b96fe5/src/scriptlets/prevent-xhr.js#L206 if response is a text then it probably should be set to modifiedResponseText.