Camera Plugin

Camera package with custom camera_android that fix crash issues.

Only On Android

````
Thread Name: 'CameraBackground'
Back traces starts.
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.hardware.camera2.CameraCaptureSession.close()' on a null object reference
at io.flutter.plugins.camera.Camera.closeCaptureSession(Camera.java:1228)
at io.flutter.plugins.camera.Camera$1.onClosed(Camera.java:348)
at android.hardware.camera2.impl.CameraDeviceImpl$5.run(CameraDeviceImpl.java:252)
at android.os.Handler.handleCallback(Handler.java:942)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:223)
at android.os.Looper.loop(Looper.java:324)
at android.os.HandlerThread.run(HandlerThread.java:67)
Back traces ends.
````

Issue

https://github.com/flutter/flutter/issues/114012

Occasionally reproduce this crash:

Continuously enter and exit the camera page, crash occurs between the 100th and 300th time.

100% Re-Produce the issue steps:

1. Set two breakpoints in io.flutter.plugins.camera.Camera Camera.java :
   • breakpoint 1: Line 1228 captureSession.close();
   • breakpoint 2: Line 1263 captureSession = null;
2. Push the camera view in then pop it out after the camera is working.
3. Continue the thread from breakpoint 2 -> breakpoint 1, crash raised.

How-to fix:

Just add synchronized key to this three close method

synchronized void closeCaptureSession() {
// on Line 1224
...

synchronized public void close() {
// on Line 1233
...

synchronized private void stopAndReleaseCamera() {
// on Line 1256
...