For EXP-3625: Hook up getCoenrollingFeatureIds to NimbusApi and NimbusBuilder for swift

components/nimbus/ios/Nimbus/NimbusApi.swift

@@ -167,6 +167,12 @@ public protocol NimbusUserConfiguration {
     /// - Returns  A list of `AvailableExperiment`s
     ///
     func getAvailableExperiments() -> [AvailableExperiment]
+
+    /// Get a list of feature ids where the feature allows co-enrollment.
+    ///
+    /// - Returns  A list of experiment ids that allow co-enrollment.
+    ///
+    func getCoenrollingFeatureIds() -> [String]
 }
 
 public protocol NimbusEventStore {

components/nimbus/ios/Nimbus/NimbusBuilder.swift

@@ -231,8 +231,7 @@ public class NimbusBuilder {
     // swiftlint:enable function_body_length
 
     func getCoenrollingFeatureIds() -> [String] {
-        // This will be changed to use the feature manifest in EXP-3265
-        []
+        featureManifest?.getCoenrollingFeatureIds() ?? []
     }
 
     func newNimbus(_ appInfo: NimbusAppSettings, serverSettings: NimbusServerSettings?) throws -> NimbusInterface {