[PM-26682] [Milestone 2d] Display discount on subscription page (#17229)

* The discount badge implementation

* Use existing flag

* Added the top spaces as requested

* refactor: move discount-badge to pricing library and consolidate discount classes

* fix: add CommonModule import to discount-badge component and simplify discounted amount calculation

- Add CommonModule import to discount-badge component for *ngIf directive
- Simplify discountedSubscriptionAmount to use upcomingInvoice.amount from server instead of manual calculation

* Fix the lint errors

* Story update

---------

Co-authored-by: Alex Morask <amorask@bitwarden.com>

apps/web/src/app/billing/shared/billing-shared.module.ts

@@ -1,6 +1,7 @@
 import { NgModule } from "@angular/core";
 
 import { BannerModule } from "@bitwarden/components";
+import { DiscountBadgeComponent } from "@bitwarden/pricing";
 import {
   EnterBillingAddressComponent,
   EnterPaymentMethodComponent,
@@ -28,6 +29,7 @@ import { UpdateLicenseComponent } from "./update-license.component";
     BannerModule,
     EnterPaymentMethodComponent,
     EnterBillingAddressComponent,
+    DiscountBadgeComponent,
   ],
   declarations: [
     BillingHistoryComponent,
@@ -51,6 +53,7 @@ import { UpdateLicenseComponent } from "./update-license.component";
     OffboardingSurveyComponent,
     IndividualSelfHostingLicenseUploaderComponent,
     OrganizationSelfHostingLicenseUploaderComponent,
+    DiscountBadgeComponent,
   ],
 })
 export class BillingSharedModule {}