iOS Swift Conversion (#2527)

Converts iOS implementation from Objective-c to Swift

# During the conversion process some updates to the code structure were also made
- Modularize codebase from single file to smaller focused files
- Untangled large nested IF statements
- Added more null checks, since Swift is more strict with null pointers
- Added property to allow for decoding of local video sources with self contained key for offline playback
- Updates example apps to test react-native 0.63.4 and uses auto native dependency imports for android and ios

ios/Video/DataStructures/TextTrack.swift

@@ -0,0 +1,25 @@
+
+struct TextTrack {
+    let type: String
+    let language: String
+    let title: String
+    let uri: String
+    
+    let json: NSDictionary?
+    
+    init(_ json: NSDictionary!) {
+        guard json != nil else {
+            self.json = nil
+            self.type = ""
+            self.language = ""
+            self.title = ""
+            self.uri = ""
+            return
+        }
+        self.json = json
+        self.type = json["type"] as? String ?? ""
+        self.language = json["language"] as? String ?? ""
+        self.title = json["title"] as? String ?? ""
+        self.uri = json["uri"] as? String ?? ""
+    }
+}