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

examples/basic/windows/VideoPlayer/AutolinkedNativeModules.g.props

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <!-- AutolinkedNativeModules.g.props contents generated by "react-native autolink-windows" -->
+  <PropertyGroup>
+  </PropertyGroup>
+</Project>