Add Privacy Config feature to control ad attribution reporting (#1042)

Please review the release process for BrowserServicesKit
[here](https://app.asana.com/0/1200194497630846/1200837094583426).

**Required**:

Task/Issue URL: https://app.asana.com/0/0/1208638248015576/f
iOS PR: duckduckgo/iOS#3506
macOS PR: duckduckgo/macos-browser#3478
What kind of version bump will this require?: Minor

**Optional**:

Tech Design URL:
CC:

**Description**:

Adds feature to control the ad attribution reporting on iOS.

**Steps to test this PR**:
See duckduckgo/iOS#3506

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**OS Testing**:

* [ ] iOS 14
* [ ] iOS 15
* [ ] iOS 16
* [ ] macOS 10.15
* [ ] macOS 11
* [ ] macOS 12

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

Sources/BrowserServicesKit/PrivacyConfig/Features/PrivacyFeature.swift

@@ -63,6 +63,7 @@ public enum PrivacyFeature: String {
     case networkProtection
     case aiChat
     case contextualOnboarding
+    case adAttributionReporting
 }
 
 /// An abstraction to be implemented by any "subfeature" of a given `PrivacyConfiguration` feature.