Use fetch helpers instead of fetch (#27026)

WIP because:

- [x] Some calls set a `content-type` but send no body, can likely
remove the header
- [x] Need to check whether `charset=utf-8` has any significance on the
webauthn calls, I assume not as it is the default for json content.
- [x] Maybe `no-restricted-globals` is better for eslint, but will
require a lot of duplication in the yaml or moving eslint config to a
`.js` extension.
- [x] Maybe export `request` as `fetch`, shadowing the global.

web_src/js/features/install.js

@@ -1,5 +1,6 @@
 import $ from 'jquery';
 import {hideElem, showElem} from '../utils/dom.js';
+import {GET} from '../modules/fetch.js';
 
 export function initInstall() {
   const $page = $('.page-content.install');
@@ -111,7 +112,7 @@ function initPostInstall() {
   const targetUrl = el.getAttribute('href');
   let tid = setInterval(async () => {
     try {
-      const resp = await fetch(targetUrl);
+      const resp = await GET(targetUrl);
       if (tid && resp.status === 200) {
         clearInterval(tid);
         tid = null;