Reland "[iOS] Enable Earl Grey 1 and 2 tests for ClearSyncedData feature."

This reverts commit fcca6197.

Reason for revert: Required downstream fix was submitted.

Original change's description:
> Revert "[iOS] Enable Earl Grey 1 and 2 tests for ClearSyncedData feature."
> 
> This reverts commit 3edb7dbb.
> 
> Reason for revert: consistently fails on downstream bots.
> 
> Original change's description:
> > [iOS] Enable Earl Grey 1 and 2 tests for ClearSyncedData feature.
> > 
> > Previously the test case testSignOutAndClearDataFromNonManagedAccountClearsData() was disabled due to a misuse of the ScopedFeatureList flag, which should only be used for unit tests. This meant that the flag was not set correctly in the tests.
> > 
> > The change uses the AppLaunchManager to enable the experimental flag on Earl Grey 2 and the flag within the Earl Grey 1 JSON setup.
> > 
> > Bug: 1045981
> > Change-Id: I3160477a5230d24617168800a5cabacb4b8fd672
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2023835
> > Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
> > Reviewed-by: Ben Pastene <bpastene@chromium.org>
> > Commit-Queue: Nohemi Fernandez <fernandex@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#737283}
> 
> TBR=sdefresne@chromium.org,bpastene@chromium.org,fernandex@chromium.org
> 
> Change-Id: I58ffda870f5d63c9b23fb9fb40903d14b2fd9ead
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 1045981
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2032120
> Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
> Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#737316}

TBR=sdefresne@chromium.org,bpastene@chromium.org,fernandex@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1045981
Change-Id: I861b7342e2407bc972e6d794ec2ad85a4cd73019
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2037993Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Mihai Sardarescu <msarda@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738519}

ios/build/bots/tests/eg_tests.json

@@ -16,6 +16,9 @@
     },
     {
       "app": "ios_chrome_settings_egtests",
+      "test args": [
+        "--enable-features=ClearSyncedData"
+      ],
       "xcode parallelization": true,
       "shards": 1,
       "swarming tasks": 3

ios/chrome/browser/ui/settings/google_services/accounts_table_egtest.mm

@@ -49,9 +49,7 @@ id<GREYMatcher> NoBookmarksLabel() {
 @interface AccountCollectionsTestCase : ChromeTestCase
 @end
 
-@implementation AccountCollectionsTestCase {
-  base::test::ScopedFeatureList _featureList;
-}
+@implementation AccountCollectionsTestCase
 
 - (void)tearDown {
   [ChromeEarlGrey waitForBookmarksToFinishLoading];
@@ -62,9 +60,14 @@ id<GREYMatcher> NoBookmarksLabel() {
   [super tearDown];
 }
 
-- (void)setUp {
-  _featureList.InitAndEnableFeature(kClearSyncedData);
+- (void)launchAppForTestMethod {
+  [[AppLaunchManager sharedManager]
+      ensureAppLaunchedWithFeaturesEnabled:{kClearSyncedData}
+                                  disabled:{}
+                            relaunchPolicy:NoForceRelaunchAndResetState];
+}
 
+- (void)setUp {
   [super setUp];
 
   [ChromeEarlGrey waitForBookmarksToFinishLoading];
@@ -205,8 +208,7 @@ id<GREYMatcher> NoBookmarksLabel() {
 
 // Tests that selecting sign-out and clear data from a non-managed user account
 // clears the user's synced data.
-// TODO(crbug.com/1045981): Fix and enable.
-- (void)DISABLED_testSignOutAndClearDataFromNonManagedAccountClearsData {
+- (void)testSignOutAndClearDataFromNonManagedAccountClearsData {
   FakeChromeIdentity* fakeIdentity = [SigninEarlGreyUtils fakeIdentity1];
 
   // Sign In |fakeIdentity|.

testing/buildbot/gn_isolate_map.pyl

@@ -917,7 +917,9 @@
     "type": "raw",
   },
   "ios_chrome_settings_egtests": {
-    "args": [],
+    "args": [
+      "--enable-features=ClearSyncedData",
+    ],
     "label": "//ios/chrome/test/earl_grey:ios_chrome_settings_egtests",
     "type": "raw",
   },