Add Codable conformance to common Foundation types

Add conformances + unit tests for

* CGFloat
* AffineTransform
* Calendar
* CharacterSet
* DateComponents
* DateInterval
* Decimal
* IndexPath
* IndexSet
* Locale
* Measurement
* NSRange
* PersonNameComponents
* TimeZone
* URL
* UUID

along with some unit tests for each.

stdlib/public/SDK/Foundation/CharacterSet.swift

@@ -807,3 +807,19 @@ extension NSCharacterSet : _HasCustomAnyHashableRepresentation {
     }
 }
 
+extension CharacterSet : Codable {
+    private enum CodingKeys : Int, CodingKey {
+        case bitmap
+    }
+
+    public init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let bitmap = try container.decode(Data.self, forKey: .bitmap)
+        self.init(bitmapRepresentation: bitmap)
+    }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(self.bitmapRepresentation, forKey: .bitmap)
+    }
+}