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.

.eslintrc.yaml

@@ -46,6 +46,9 @@ overrides:
   - files: ["*.config.*"]
     rules:
       import/no-unused-modules: [0]
+  - files: ["web_src/js/modules/fetch.js", "web_src/js/standalone/**/*"]
+    rules:
+      no-restricted-syntax: [2, WithStatement, ForInStatement, LabeledStatement, SequenceExpression]
 
 rules:
   "@eslint-community/eslint-comments/disable-enable-pair": [2]
@@ -420,7 +423,7 @@ rules:
   no-restricted-exports: [0]
   no-restricted-globals: [2, addEventListener, blur, close, closed, confirm, defaultStatus, defaultstatus, error, event, external, find, focus, frameElement, frames, history, innerHeight, innerWidth, isFinite, isNaN, length, location, locationbar, menubar, moveBy, moveTo, name, onblur, onerror, onfocus, onload, onresize, onunload, open, opener, opera, outerHeight, outerWidth, pageXOffset, pageYOffset, parent, print, removeEventListener, resizeBy, resizeTo, screen, screenLeft, screenTop, screenX, screenY, scroll, scrollbars, scrollBy, scrollTo, scrollX, scrollY, self, status, statusbar, stop, toolbar, top, __dirname, __filename]
   no-restricted-imports: [0]
-  no-restricted-syntax: [2, WithStatement, ForInStatement, LabeledStatement, SequenceExpression]
+  no-restricted-syntax: [2, WithStatement, ForInStatement, LabeledStatement, SequenceExpression, {selector: "CallExpression[callee.name='fetch']", message: "use modules/fetch.js instead"}]
   no-return-assign: [0]
   no-script-url: [2]
   no-self-assign: [2, {props: true}]