feat: New Core/ library (#1975)

Moves everything Camera related into `core/` / `Core/` so that it is better encapsulated from React Native.

Benefits:

1. Code is much better organized. Should be easier for collaborators now, and cleaner codebase for me.
2. Locking is fully atomically as you can now only configure the session through a lock/Mutex which is batch-overridable
    * On iOS, this makes Camera startup time **MUCH** faster, I measured speedups from **1.5 seconds** to only **240 milliseconds** since we only lock/commit once! 🚀 
    * On Android, this fixes a few out-of-sync/concurrency issues like "Capture Request contains unconfigured Input/Output Surface!" since it is now a single lock-operation! 💪 
3. It is easier to integrate VisionCamera outside of React Native (e.g. Native iOS Apps, NativeScript, Flutter, etc)

With this PR, VisionCamera V3 is up to **7x** faster than V2

package/ios/Core/CameraQueues.swift

@@ -0,0 +1,40 @@
+//
+//  CameraQueues.swift
+//  VisionCamera
+//
+//  Created by Marc Rousavy on 22.03.21.
+//  Copyright © 2021 mrousavy. All rights reserved.
+//
+
+import Foundation
+
+@objc
+public class CameraQueues: NSObject {
+  /// The serial execution queue for camera configuration and setup.
+  @objc public static let cameraQueue = DispatchQueue(label: "mrousavy/VisionCamera.main",
+                                                      qos: .userInteractive,
+                                                      attributes: [],
+                                                      autoreleaseFrequency: .inherit,
+                                                      target: nil)
+
+  /// The serial execution queue for output processing of videos for recording or synchronous frame processing.
+  @objc public static let videoQueue = DispatchQueue(label: "mrousavy/VisionCamera.video",
+                                                     qos: .userInteractive,
+                                                     attributes: [],
+                                                     autoreleaseFrequency: .inherit,
+                                                     target: nil)
+
+  /// The serial execution queue for output processing of QR/barcodes.
+  @objc public static let codeScannerQueue = DispatchQueue(label: "mrousavy/VisionCamera.codeScanner",
+                                                           qos: .userInteractive,
+                                                           attributes: [],
+                                                           autoreleaseFrequency: .inherit,
+                                                           target: nil)
+
+  /// The serial execution queue for output processing of audio buffers.
+  @objc public static let audioQueue = DispatchQueue(label: "mrousavy/VisionCamera.audio",
+                                                     qos: .userInteractive,
+                                                     attributes: [],
+                                                     autoreleaseFrequency: .inherit,
+                                                     target: nil)
+}