[iOS] Clean up inactive tabs flag

This CL cleans up the inactive tabs flag:
 - Remove the flag for iPhone
 - Make it default-disabled on iPad
 - Remove the threshold arguments and use a system setting instead
 - Use a fake system setting for test threshold
 - Update the tests to use new flags
 - Light cleanup
 - Delete the unit test checking the priority of the setting on the
   flag

Bug: 375190996
Change-Id: I03ceb075bfe35f0267f80670ac18bac55bf05eda
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5953259
Commit-Queue: Gauthier Ambard <[email protected]>
Reviewed-by: Louis Romero <[email protected]>
Auto-Submit: Gauthier Ambard <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1373362}
diff --git a/ios/chrome/browser/flags/about_flags.mm b/ios/chrome/browser/flags/about_flags.mm
index 975f5eb..c213d63 100644
--- a/ios/chrome/browser/flags/about_flags.mm
+++ b/ios/chrome/browser/flags/about_flags.mm
@@ -382,30 +382,6 @@
         {"Long-Press and One-Tap", kEnableExpKitTextClassifierEmailOneTap,
          std::size(kEnableExpKitTextClassifierEmailOneTap), nullptr}};
 
-const FeatureEntry::FeatureParam kTabInactivityThresholdOneWeek[] = {
-    {kTabInactivityThresholdParameterName,
-     kTabInactivityThresholdOneWeekParam}};
-const FeatureEntry::FeatureParam kTabInactivityThresholdTwoWeeks[] = {
-    {kTabInactivityThresholdParameterName,
-     kTabInactivityThresholdTwoWeeksParam}};
-const FeatureEntry::FeatureParam kTabInactivityThresholdThreeWeeks[] = {
-    {kTabInactivityThresholdParameterName,
-     kTabInactivityThresholdThreeWeeksParam}};
-const FeatureEntry::FeatureParam kTabInactivityThresholdOneMinuteDemo[] = {
-    {kTabInactivityThresholdParameterName,
-     kTabInactivityThresholdOneMinuteDemoParam}};
-
-const FeatureEntry::FeatureVariation kTabInactivityThresholdVariations[] = {
-    {"One week", kTabInactivityThresholdOneWeek,
-     std::size(kTabInactivityThresholdOneWeek), nullptr},
-    {"Two weeks", kTabInactivityThresholdTwoWeeks,
-     std::size(kTabInactivityThresholdTwoWeeks), nullptr},
-    {"Three weeks", kTabInactivityThresholdThreeWeeks,
-     std::size(kTabInactivityThresholdThreeWeeks), nullptr},
-    {"One minute [Demo]", kTabInactivityThresholdOneMinuteDemo,
-     std::size(kTabInactivityThresholdOneMinuteDemo), nullptr},
-};
-
 const FeatureEntry::FeatureParam kTabResumptionMostRecentTabOnly[] = {
     {kTabResumptionParameterName, kTabResumptionMostRecentTabOnlyParam}};
 const FeatureEntry::FeatureParam kTabResumptionAllTabs[] = {
@@ -1495,11 +1471,9 @@
      commerce::flag_descriptions::kCommerceLocalPDPDetectionDescription,
      flags_ui::kOsIos,
      FEATURE_VALUE_TYPE(commerce::kCommerceLocalPDPDetection)},
-    {"tab-inactivity-threshold", flag_descriptions::kTabInactivityThresholdName,
-     flag_descriptions::kTabInactivityThresholdDescription, flags_ui::kOsIos,
-     FEATURE_WITH_PARAMS_VALUE_TYPE(kTabInactivityThreshold,
-                                    kTabInactivityThresholdVariations,
-                                    "TabInactivityThreshold")},
+    {"inactive-tabs", flag_descriptions::kInactiveTabsIPadName,
+     flag_descriptions::kInactiveTabsIPadDescription, flags_ui::kOsIos,
+     FEATURE_VALUE_TYPE(kInactiveTabsIPadFeature)},
     {"notification-settings-menu-item",
      flag_descriptions::kNotificationSettingsMenuItemName,
      flag_descriptions::kNotificationSettingsMenuItemDescription,