Imports necessary for Glean to work in the iOS megazord again

glean-core/ios/Glean/Glean.swift

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import Foundation
+import UIKit
 
 private typealias GleanBaseline = GleanMetrics.GleanBaseline
 private typealias GleanInternalMetrics = GleanMetrics.GleanInternalMetrics

glean-core/ios/Glean/Metrics/DatetimeMetric.swift

@@ -2,6 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+import Foundation
+
 /// This implements the developer facing API for recording datetime metrics.
 ///
 /// Instances of this class type are automatically generated by the parsers at build time,

glean-core/ios/Glean/Metrics/UrlMetric.swift

@@ -2,6 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+import Foundation
+
 /// This implements the developer facing API for recording URL metrics.
 ///
 /// Instances of this class type are automatically generated by the parsers at build time,

glean-core/ios/Glean/Metrics/UuidMetric.swift

@@ -2,6 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+import Foundation
+
 /// This implements the developer facing API for recording UUID metrics.
 ///
 /// Instances of this class type are automatically generated by the parsers at build time,

glean-core/ios/Glean/Net/HttpPingUploader.swift

@@ -2,6 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+import Foundation
+
 /// This class represents a ping uploader via HTTP.
 ///
 /// This will typically be invoked by the appropriate scheduling mechanism to upload a ping to the server.

glean-core/ios/Glean/Scheduler/GleanLifecycleObserver.swift

@@ -2,6 +2,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+import Foundation
+import UIKit
+
 private typealias GleanBaseline = GleanMetrics.GleanBaseline
 
 class GleanLifecycleObserver {

glean-core/ios/Glean/Scheduler/MetricsPingScheduler.swift

@@ -2,6 +2,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+import Foundation
+import UIKit
+
 /// MetricsPingScheduler facilitates scheduling the periodic assembling of metrics pings,
 /// at a given time, trying its best to handle the following cases:
 ///