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/CameraSession+CodeScanner.swift

@@ -0,0 +1,80 @@
+//
+//  CameraSession+CodeScanner.swift
+//  VisionCamera
+//
+//  Created by Marc Rousavy on 11.10.23.
+//  Copyright © 2023 mrousavy. All rights reserved.
+//
+
+import AVFoundation
+import Foundation
+
+extension CameraSession: AVCaptureMetadataOutputObjectsDelegate {
+  public func metadataOutput(_: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from _: AVCaptureConnection) {
+    guard let onCodeScanned = delegate?.onCodeScanned else {
+      // No delegate callback
+      return
+    }
+    guard !metadataObjects.isEmpty else {
+      // No codes detected
+      return
+    }
+    guard let device = videoDeviceInput?.device else {
+      // No cameraId set
+      return
+    }
+    let size = device.activeFormat.videoDimensions
+
+    // Map codes to JS values
+    let codes = metadataObjects.map { object in
+      var value: String?
+      if let code = object as? AVMetadataMachineReadableCodeObject {
+        value = code.stringValue
+      }
+      let x = object.bounds.origin.x * Double(size.width)
+      let y = object.bounds.origin.y * Double(size.height)
+      let w = object.bounds.width * Double(size.width)
+      let h = object.bounds.height * Double(size.height)
+      let frame = CGRect(x: x, y: y, width: w, height: h)
+
+      return Code(type: object.type, value: value, frame: frame)
+    }
+
+    // Call delegate (JS) event
+    onCodeScanned(codes)
+  }
+
+  /**
+   A scanned QR/Barcode.
+   */
+  struct Code {
+    /**
+     Type of the scanned Code
+     */
+    let type: AVMetadataObject.ObjectType
+    /**
+     Decoded value of the code
+     */
+    let value: String?
+    /**
+     Location of the code on-screen, relative to the video output layer
+     */
+    let frame: CGRect
+
+    /**
+     Converts this Code to a JS Object (Dictionary)
+     */
+    func toJSValue() -> [String: AnyHashable] {
+      return [
+        "type": type.descriptor,
+        "value": value,
+        "frame": [
+          "x": frame.origin.x,
+          "y": frame.origin.y,
+          "width": frame.size.width,
+          "height": frame.size.height,
+        ],
+      ]
+    }
+  }
+}