Refactor billing process in e2e tests

Code for billing process was refactored in end-to-end tests for clean code and better structure. In the described tests, related codes and classes have been moved to a new class named BillingPageObject. All corresponding calls were updated accordingly.

packages/billing/gateway/src/components/current-plan-badge.tsx

@@ -45,7 +45,7 @@ export function CurrentPlanBadge(
   }
 
   return (
-    <Badge variant={variant}>
+    <Badge data-test={'current-plan-card-status-badge'} variant={variant}>
       <Trans i18nKey={text} />
     </Badge>
   );

packages/billing/gateway/src/components/current-subscription-card.tsx

@@ -73,7 +73,9 @@ export function CurrentSubscriptionCard({
               }
             />
 
-            <span>{product.name}</span>
+            <span data-test={'current-plan-card-product-name'}>
+              {product.name}
+            </span>
 
             <CurrentPlanBadge status={subscription.status} />
           </div>
@@ -84,7 +86,7 @@ export function CurrentSubscriptionCard({
           (e.g. trial ending soon, subscription canceled, etc.)
         */}
         <If condition={!subscription.active}>
-          <div>
+          <div data-test={'current-plan-card-status-alert'}>
             <CurrentPlanAlert status={subscription.status} />
           </div>
         </If>