Send pixel on sync secure storage read failure (#3530)

Task/Issue URL:
https://app.asana.com/0/1201493110486074/1208686320819590/f

**Description**:

On investigating a hard-to-reproduce issue with sync, I noticed there's
a gap in error reporting when the secure storage (keychain) is not
available. This adds a pixel for that case.

**Steps to test this PR**:
Just a pixel in an error case. Hard to test without altering code. But
if you do want to do that:
1. Enable sync
2. Change `BSK.DDGSync.SecureStorage.account()` to throw every time
3. Go to the Settings -> Sync screen
4. You should see the `sync_secure_storage_read_error` Pixel in the
debug console

**Definition of Done (Internal Only)**:

* [ ] Does this PR satisfy our [Definition of
Done](https://app.asana.com/0/1202500774821704/1207634633537039/f)?

**Copy Testing**:

* [ ] Use of correct apostrophes in new copy, ie `’` rather than `'`

**Orientation Testing**:

* [ ] Portrait
* [ ] Landscape

**Device Testing**:

* [ ] iPhone SE (1st Gen)
* [ ] iPhone 8
* [ ] iPhone X
* [ ] iPhone 14 Pro
* [ ] iPad

**OS Testing**:

* [ ] iOS 15
* [ ] iOS 16
* [ ] iOS 17

**Theme Testing**:

* [ ] Light theme
* [ ] Dark theme

---
###### Internal references:
[Software Engineering
Expectations](https://app.asana.com/0/59792373528535/199064865822552)
[Technical Design
Template](https://app.asana.com/0/59792373528535/184709971311943)

Author: graeme

Core/PixelEvent.swift

@@ -624,6 +624,7 @@ extension Pixel {
         case syncRemoveDeviceError
         case syncDeleteAccountError
         case syncLoginExistingAccountError
+        case syncSecureStorageReadError
 
         case syncGetOtherDevices
         case syncGetOtherDevicesCopy
@@ -1432,6 +1433,7 @@ extension Pixel.Event {
         case .syncRemoveDeviceError: return "m_d_sync_remove_device_error"
         case .syncDeleteAccountError: return "m_d_sync_delete_account_error"
         case .syncLoginExistingAccountError: return "m_d_sync_login_existing_account_error"
+        case .syncSecureStorageReadError: return "m_d_sync_secure_storage_error"
 
         case .syncGetOtherDevices: return "sync_get_other_devices"
         case .syncGetOtherDevicesCopy: return "sync_get_other_devices_copy"

Core/SyncErrorHandler.swift

@@ -100,6 +100,8 @@ public class SyncErrorHandler: EventMapping<SyncError> {
                 Pixel.fire(pixel: .syncFailedToLoadAccount, error: error)
             case .failedToSetupEngine:
                 Pixel.fire(pixel: .syncFailedToSetupEngine, error: error)
+            case .failedToReadSecureStore:
+                Pixel.fire(pixel: .syncSecureStorageReadError, error: error)
             default:
                 // Should this be so generic?
                 let domainEvent = Pixel.Event.syncSentUnauthenticatedRequest

DuckDuckGo.xcodeproj/project.pbxproj

@@ -10970,7 +10970,7 @@
 			repositoryURL = "https://github.com/DuckDuckGo/BrowserServicesKit";
 			requirement = {
 				kind = exactVersion;
-				version = 203.1.0;
+				version = 203.2.0;
 			};
 		};
 		9F8FE9472BAE50E50071E372 /* XCRemoteSwiftPackageReference "lottie-spm" */ = {