Add support for Face ID/Touch ID to app lock. (#1966)

* Fix biometrics with low grace period and backgrounding before unlocked.

* Trigger permissions alert when enabling Face ID.

ElementX/Sources/Screens/AppLock/AppLockScreen/AppLockScreenViewModel.swift

@@ -46,11 +46,7 @@ class AppLockScreenViewModel: AppLockScreenViewModelType, AppLockScreenViewModel
         
         switch viewAction {
         case .submitPINCode:
-            guard appLockService.unlock(with: state.bindings.pinCode) else {
-                handleInvalidPIN()
-                return
-            }
-            actionsSubject.send(.appUnlocked)
+            submitPINCode()
         case .clearPINCode:
             state.bindings.pinCode = ""
         case .forgotPIN:
@@ -60,6 +56,14 @@ class AppLockScreenViewModel: AppLockScreenViewModelType, AppLockScreenViewModel
     
     // MARK: - Private
     
+    private func submitPINCode() {
+        guard appLockService.unlock(with: state.bindings.pinCode) else {
+            handleInvalidPIN()
+            return
+        }
+        actionsSubject.send(.appUnlocked)
+    }
+    
     private func handleForgotPIN() {
         state.bindings.alertInfo = .init(id: .confirmResetPIN,
                                          title: L10n.screenAppLockSignoutAlertTitle,