[iOS] Ensure local state is commited on app background

Also adds a commit immediately after setting p3a enabled

ios/app/brave_core_main.mm

@@ -212,8 +212,12 @@ const BraveCoreLogSeverity BraveCoreLogSeverityVerbose =
 
 - (void)onAppEnterBackground:(NSNotification*)notification {
   auto* context = GetApplicationContext();
-  if (context)
+  if (context) {
     context->OnAppEnterBackground();
+    // Since we don't use the WebViewWebMainParts, local state is never commited
+    // on app background
+    context->GetLocalState()->CommitPendingWrite();
+  }
 }
 
 - (void)onAppEnterForeground:(NSNotification*)notification {
@@ -223,6 +227,9 @@ const BraveCoreLogSeverity BraveCoreLogSeverityVerbose =
 }
 
 - (void)onAppWillTerminate:(NSNotification*)notification {
+  // ApplicationContextImpl doesn't get teardown call at the moment because we
+  // cannot dealloc this class yet without crashing.
+  GetApplicationContext()->GetLocalState()->CommitPendingWrite();
   [[NSNotificationCenter defaultCenter] removeObserver:self];
 }
 

ios/browser/api/p3a/brave_p3a_utils.mm

@@ -38,6 +38,7 @@
 
 - (void)setIsP3AEnabled:(bool)isP3AEnabled {
   _localState->SetBoolean(brave::kP3AEnabled, isP3AEnabled);
+  _localState->CommitPendingWrite();
 }
 
 - (bool)isNoticeAcknowledged {
@@ -46,6 +47,7 @@
 
 - (void)setIsNoticeAcknowledged:(bool)isNoticeAcknowledged {
   _localState->SetBoolean(brave::kP3ANoticeAcknowledged, isNoticeAcknowledged);
+  _localState->CommitPendingWrite();
 }
 
 - (BraveHistogramsController*)histogramsController {