Paywalls: avoid flickering when displaying paywalls with available …

…cache (#3283)

Depends on #3274.

### Before:

https://github.com/RevenueCat/purchases-ios/assets/685609/d4a4e78b-69ca-4288-97a5-3168867758ef

### After:

https://github.com/RevenueCat/purchases-ios/assets/685609/1c23c50b-e802-4b25-b9a3-30b8ea27b84e

### Before loading frame:

![image](https://github.com/RevenueCat/purchases-ios/assets/685609/fe278631-bdbe-44d6-b661-7a5c259bb40d)

RevenueCatUI/PaywallView.swift

@@ -82,10 +82,14 @@ public struct PaywallView: View {
         introEligibility: TrialOrIntroEligibilityChecker?,
         purchaseHandler: PurchaseHandler?
     ) {
-        self._offering = .init(initialValue: offering)
-        self._customerInfo = .init(initialValue: customerInfo)
         self._introEligibility = .init(wrappedValue: introEligibility ?? .default())
         self._purchaseHandler = .init(wrappedValue: purchaseHandler ?? .default())
+        self._offering = .init(
+            initialValue: offering ?? Self.loadCachedCurrentOfferingIfPossible()
+        )
+        self._customerInfo = .init(
+            initialValue: customerInfo ?? Self.loadCachedCustomerInfoIfPossible()
+        )
         self.mode = mode
         self.fonts = fonts
     }
@@ -176,6 +180,32 @@ public struct PaywallView: View {
 
 }
 
+@available(iOS 15.0, macOS 12.0, tvOS 15.0, *)
+@available(watchOS, unavailable)
+@available(macOS, unavailable)
+@available(tvOS, unavailable)
+private extension PaywallView {
+
+    static func loadCachedCustomerInfoIfPossible() -> CustomerInfo? {
+        if Purchases.isConfigured {
+            return Purchases.shared.cachedCustomerInfo
+        } else {
+            return nil
+        }
+    }
+
+    static func loadCachedCurrentOfferingIfPossible() -> Offering? {
+        if Purchases.isConfigured {
+            return Purchases.shared.cachedOfferings?.current
+        } else {
+            return nil
+        }
+    }
+
+}
+
+// MARK: -
+
 @available(iOS 15.0, macOS 12.0, tvOS 15.0, *)
 @available(tvOS, unavailable)
 struct LoadedOfferingPaywallView: View {
@@ -357,19 +387,4 @@ private extension PaywallViewMode {
 
 }
 
-@available(iOS 15.0, macOS 12.0, tvOS 15.0, *)
-private extension PaywallTemplate {
-
-    var name: String {
-        switch self {
-        case .template1: return "Minimalist"
-        case .template2: return "Bold Packages"
-        case .template3: return "Feature List"
-        case .template4: return "Horizontal"
-        case .template5: return "Small Banner"
-        }
-    }
-
-}
-
 #endif