fix(client-utils): only call fetch as a function, not a method (#10671

)

closes: #XXXX
refs: endojs/endo#31 (comment)

## Description

Testing on Brave, the browser's global `fetch` function works when called with its `this` bound to either `undefined` or the browser global object, but does not work if its `this` is bound to something else. The code this PR fixes was misbehaving because it was calling `powers.fetch(...)`, i.e., happening to call it as a method with its `this` bound to the irrelevant `powers` object.

This refactor just expresses the intention of this code, which is just to call the `fetch` function without passing it some object as its `this` binding. This seems to fix the problem.

Not at all addressed by this PR: The fact that this problem happened from a programming patterns that seems correct and would have passed review indicates a deeper hazard. This PR does nothing to mitigate this deeper hazard. It only fixes this case where we fell into the hazard.

### Security Considerations

none

### Scaling Considerations
none

### Documentation Considerations
none, except as needed to address the more general hazard.

### Testing Considerations
Only tested `fetch` behavior on Brave. Based on that, proceeding under untested assumption that this refactor will work on all supported browsers.

### Upgrade Considerations
none

a3p-integration/proposals/z:acceptance/test-lib/rpc.js

@@ -43,12 +43,12 @@ export { networkConfig };
  * @param {typeof window.fetch} powers.fetch
  * @param {MinimalNetworkConfig} config
  */
-export const makeVStorage = (powers, config = networkConfig) => {
+export const makeVStorage = ({ fetch }, config = networkConfig) => {
   /** @param {string} path */
   const getJSON = path => {
     const url = config.rpcAddrs[0] + path;
     // console.warn('fetching', url);
-    return powers.fetch(url, { keepalive: true }).then(res => res.json());
+    return fetch(url, { keepalive: true }).then(res => res.json());
   };
   // height=0 is the same as omitting height and implies the highest block
   const url = (path = 'published', { kind = 'children', height = 0 } = {}) =>

packages/client-utils/src/vstorage.js

@@ -9,12 +9,12 @@
  * @param {typeof window.fetch} powers.fetch
  * @param {MinimalNetworkConfig} config
  */
-export const makeVStorage = (powers, config) => {
+export const makeVStorage = ({ fetch }, config) => {
   /** @param {string} path */
   const getJSON = path => {
     const url = config.rpcAddrs[0] + path;
     // console.warn('fetching', url);
-    return powers.fetch(url, { keepalive: true }).then(res => res.json());
+    return fetch(url, { keepalive: true }).then(res => res.json());
   };
   // height=0 is the same as omitting height and implies the highest block
   const url = (path = 'published', { kind = 'children', height = 0 } = {}) =>