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/PhotoCaptureDelegate.swift

@@ -0,0 +1,115 @@
+//
+//  PhotoCaptureDelegate.swift
+//  mrousavy
+//
+//  Created by Marc Rousavy on 15.12.20.
+//  Copyright © 2020 mrousavy. All rights reserved.
+//
+
+import AVFoundation
+
+// Keeps a strong reference on delegates, as the AVCapturePhotoOutput only holds a weak reference.
+private var delegatesReferences: [NSObject] = []
+
+// MARK: - PhotoCaptureDelegate
+
+class PhotoCaptureDelegate: NSObject, AVCapturePhotoCaptureDelegate {
+  private let promise: Promise
+  private let enableShutterSound: Bool
+
+  required init(promise: Promise, enableShutterSound: Bool) {
+    self.promise = promise
+    self.enableShutterSound = enableShutterSound
+    super.init()
+    delegatesReferences.append(self)
+  }
+
+  func photoOutput(_: AVCapturePhotoOutput, willCapturePhotoFor _: AVCaptureResolvedPhotoSettings) {
+    if !enableShutterSound {
+      // disable system shutter sound (see https://stackoverflow.com/a/55235949/5281431)
+      AudioServicesDisposeSystemSoundID(1108)
+    }
+  }
+
+  func photoOutput(_: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
+    defer {
+      delegatesReferences.removeAll(where: { $0 == self })
+    }
+    if let error = error as NSError? {
+      promise.reject(error: .capture(.unknown(message: error.description)), cause: error)
+      return
+    }
+
+    let error = ErrorPointer(nilLiteral: ())
+    guard let tempFilePath = RCTTempFilePath("jpeg", error)
+    else {
+      let message = error?.pointee?.description
+      promise.reject(error: .capture(.createTempFileError(message: message)), cause: error?.pointee)
+      return
+    }
+    let url = URL(string: "file://\(tempFilePath)")!
+
+    guard let data = photo.fileDataRepresentation() else {
+      promise.reject(error: .capture(.fileError))
+      return
+    }
+
+    do {
+      try data.write(to: url)
+      let exif = photo.metadata["{Exif}"] as? [String: Any]
+      let width = exif?["PixelXDimension"]
+      let height = exif?["PixelYDimension"]
+      let exifOrientation = photo.metadata[String(kCGImagePropertyOrientation)] as? UInt32 ?? CGImagePropertyOrientation.up.rawValue
+      let cgOrientation = CGImagePropertyOrientation(rawValue: exifOrientation) ?? CGImagePropertyOrientation.up
+      let orientation = getOrientation(forExifOrientation: cgOrientation)
+      let isMirrored = getIsMirrored(forExifOrientation: cgOrientation)
+
+      promise.resolve([
+        "path": tempFilePath,
+        "width": width as Any,
+        "height": height as Any,
+        "orientation": orientation,
+        "isMirrored": isMirrored,
+        "isRawPhoto": photo.isRawPhoto,
+        "metadata": photo.metadata,
+        "thumbnail": photo.embeddedThumbnailPhotoFormat as Any,
+      ])
+    } catch {
+      promise.reject(error: .capture(.fileError), cause: error as NSError)
+    }
+  }
+
+  func photoOutput(_: AVCapturePhotoOutput, didFinishCaptureFor _: AVCaptureResolvedPhotoSettings, error: Error?) {
+    defer {
+      delegatesReferences.removeAll(where: { $0 == self })
+    }
+    if let error = error as NSError? {
+      promise.reject(error: .capture(.unknown(message: error.description)), cause: error)
+      return
+    }
+  }
+
+  private func getOrientation(forExifOrientation exifOrientation: CGImagePropertyOrientation) -> String {
+    switch exifOrientation {
+    case .up, .upMirrored:
+      return "portrait"
+    case .down, .downMirrored:
+      return "portrait-upside-down"
+    case .left, .leftMirrored:
+      return "landscape-left"
+    case .right, .rightMirrored:
+      return "landscape-right"
+    default:
+      return "portrait"
+    }
+  }
+
+  private func getIsMirrored(forExifOrientation exifOrientation: CGImagePropertyOrientation) -> Bool {
+    switch exifOrientation {
+    case .upMirrored, .rightMirrored, .downMirrored, .leftMirrored:
+      return true
+    default:
+      return false
+    }
+  }
+}