Pay Anything RC Fixes (#2511)

* feat: Swap flow for Pay Anything. [WIP]

* feat: Pay Anything Swap Flow [WIP]

* feat: Pay anything swap flow [WIP]
- Add fiat values for send and receive amounts to swap details confirmation bottomsheet

* feat: Pay anything swap flow [WIP]
- Switch exchangeviewmodel back to factory
- Expand address box to fill width

* Handle second swipe to swap cta

* Add fiat for receive amount

* Scope Observers for bottomsheets and add validator

* fix: Repeated instances issue for exchangeVM

* fix: Estimated fee and balance not correctly updating after wallet switching occurs

* fix: Available balance not updating properly after wallet switching

* fix: Available balance and fee rate not displaying after wallet is switched in pay anything flow

* fixes: Pay anything related RC fixes
- Recieve fiat amount showing as 0.0
- ID overlapping when there's enough space
- receive amount changing even in fixed rate mode
- Invalid double error for setReceiveFiatAmount

lib/view_model/exchange/exchange_trade_view_model.dart

@@ -127,16 +127,16 @@ abstract class ExchangeTradeViewModelBase with Store {
   @computed
   bool get isFiatDisabled => feesViewModel.isFiatDisabled;
 
-  @computed
-  String get receiveAmountFiatFormatted {
+  @action
+  String getReceiveAmountFiatFormatted(String receiveAmount) {
     var amount = '0.00';
     try {
-      if (trade.receiveAmount?.isNotEmpty ?? false) {
+      if (receiveAmount.isNotEmpty) {
         if (fiatConversionStore.prices[trade.to] == null) return '';
 
         amount = calculateFiatAmount(
           price: fiatConversionStore.prices[trade.to]!,
-          cryptoAmount: trade.receiveAmount,
+          cryptoAmount: receiveAmount,
         );
       }
     } catch (_) {

lib/view_model/exchange/exchange_view_model.dart

@@ -24,7 +24,6 @@ import 'package:cake_wallet/exchange/provider/chainflip_exchange_provider.dart';
 import 'package:cake_wallet/exchange/provider/changenow_exchange_provider.dart';
 import 'package:cake_wallet/exchange/provider/exchange_provider.dart';
 import 'package:cake_wallet/exchange/provider/exolix_exchange_provider.dart';
-import 'package:cake_wallet/exchange/provider/letsexchange_exchange_provider.dart';
 import 'package:cake_wallet/exchange/provider/sideshift_exchange_provider.dart';
 import 'package:cake_wallet/exchange/provider/stealth_ex_exchange_provider.dart';
 import 'package:cake_wallet/exchange/provider/swaptrade_exchange_provider.dart';
@@ -449,8 +448,8 @@ abstract class ExchangeViewModelBase extends WalletChangeListenerViewModel with
 
   @action
   void setReceiveAmountFromFiat({required String fiatAmount}) {
-    final crypto = double.parse(fiatAmount.replaceAll(',', '.')) /
-        fiatConversionStore.prices[receiveCurrency]!;
+    final _enteredAmount = double.tryParse(fiatAmount.replaceAll(',', '.')) ?? 0.0;
+    final crypto = _enteredAmount / fiatConversionStore.prices[receiveCurrency]!;
     final receiveAmountTmp = _cryptoNumberFormat.format(crypto);
     if (receiveAmount != receiveAmountTmp) {
       changeReceiveAmount(amount: receiveAmountTmp);
@@ -467,6 +466,10 @@ abstract class ExchangeViewModelBase extends WalletChangeListenerViewModel with
       return;
     }
 
+    /// For fixed-rate transactions, we don't want to recalculate receive amount
+    /// as it should remain exactly what the user set
+    if (isFixedRateMode) return;
+
     final _enteredAmount = double.tryParse(amount.replaceAll(',', '.')) ?? 0;
 
     /// in case the best rate was not calculated yet
@@ -475,6 +478,7 @@ abstract class ExchangeViewModelBase extends WalletChangeListenerViewModel with
 
       await calculateBestRate();
     }
+
     _cryptoNumberFormat.maximumFractionDigits = receiveMaxDigits;
 
     receiveAmount = _cryptoNumberFormat