[deprecate-unload] Fix fetch keepalive related WPTs

The following targets explicitly test some behaviors within unload:

- external/wpt/fetch/api/basic/keepalive.any.js
- external/wpt/fetch/api/cors/cors-keepalive.any.js
- external/wpt/fetch/api/redirect/redirect-keepalive.any.js
- external/wpt/fetch/metadata/unload.https.sub.html

This CL added these WPTs to the virtual test suite `deprecate-unload`:
they are expected to either timeout or fail, as the unload handler is
not available in the virtual test suite.

Also explicitly set `--disable-features=DeprecateUnload` for the other
existing virtual test suites that cover these WPT targets.

Bug: 1488371
Change-Id: I40c8b1829e8bca7398a85d634a1ee04e585600b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5028677
Reviewed-by: Xianzhu Wang <[email protected]>
Reviewed-by: Fergal Daly <[email protected]>
Commit-Queue: Ming-Ying Chung <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1225933}

fetch/api/resources/keepalive-helper.js

@@ -93,14 +93,12 @@ function assertStashedTokenAsync(
         }))
         .then(test.step_func(result => {
           if (expectTokenExist) {
-            assert_equals(
-                result, 'on', `token [${token}] should be on (stashed).`);
+            assert_equals(result, 'on', `token should be on (stashed).`);
             test.done();
           } else {
             assert_not_equals(
-                result, 'on', `token [${token}] should not be on (stashed).`);
-            return Promise.reject(
-                `Failed to retrieve token [${token}] from server`);
+                result, 'on', `token should not be on (stashed).`);
+            return Promise.reject(`Failed to retrieve token from server`);
           }
         }))
         .catch(test.step_func(e => {