Update price display (#4736)

* Update price display

As proposed by @dstrukt in #4364.

* Update format

* Unify price display across the app

* Add DisplayFormatter

* Replace DisplayFormatCurrency method

* Use symbol currency format for invoice

* Unify currency formats on backend pages

* Revert recent changes

* Do not show exchange rate and fiat order amount for crypto denominations

* Fix test and add test cases

BTCPayServer/Controllers/UIInvoiceController.cs

@@ -45,6 +45,7 @@ namespace BTCPayServer.Controllers
         readonly StoreRepository _StoreRepository;
         readonly UserManager<ApplicationUser> _UserManager;
         private readonly CurrencyNameTable _CurrencyNameTable;
+        private readonly DisplayFormatter _displayFormatter;
         readonly EventAggregator _EventAggregator;
         readonly BTCPayNetworkProvider _NetworkProvider;
         private readonly PaymentMethodHandlerDictionary _paymentMethodHandlerDictionary;
@@ -61,6 +62,7 @@ namespace BTCPayServer.Controllers
         public UIInvoiceController(
             InvoiceRepository invoiceRepository,
             WalletRepository walletRepository,
+            DisplayFormatter displayFormatter,
             CurrencyNameTable currencyNameTable,
             UserManager<ApplicationUser> userManager,
             RateFetcher rateProvider,
@@ -78,6 +80,7 @@ namespace BTCPayServer.Controllers
             InvoiceActivator invoiceActivator,
             LinkGenerator linkGenerator)
         {
+            _displayFormatter = displayFormatter;
             _CurrencyNameTable = currencyNameTable ?? throw new ArgumentNullException(nameof(currencyNameTable));
             _StoreRepository = storeRepository ?? throw new ArgumentNullException(nameof(storeRepository));
             _InvoiceRepository = invoiceRepository ?? throw new ArgumentNullException(nameof(invoiceRepository));