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/pull-view-file.js

@@ -1,7 +1,8 @@
 import {diffTreeStore} from '../modules/stores.js';
 import {setFileFolding} from './file-fold.js';
+import {POST} from '../modules/fetch.js';
 
-const {csrfToken, pageData} = window.config;
+const {pageData} = window.config;
 const prReview = pageData.prReview || {};
 const viewedStyleClass = 'viewed-file-checked-form';
 const viewedCheckboxSelector = '.viewed-file-form'; // Selector under which all "Viewed" checkbox forms can be found
@@ -68,11 +69,7 @@ export function initViewedCheckboxListenerFor() {
       const data = {files};
       const headCommitSHA = form.getAttribute('data-headcommit');
       if (headCommitSHA) data.headCommitSHA = headCommitSHA;
-      fetch(form.getAttribute('data-link'), {
-        method: 'POST',
-        headers: {'X-Csrf-Token': csrfToken},
-        body: JSON.stringify(data),
-      });
+      POST(form.getAttribute('data-link'), {data});
 
       // Fold the file accordingly
       const parentBox = form.closest('.diff-file-header');