Remove unnecessary memory consuming temp bitmap

[kreativityapps]

On Android tmpBitmap consumes unnecessary memory in rotate and flip and there is no need for it.

This change halves the memory consumption avoiding oom issues.

[AlexV525]

Thanks for the improvement. Do you have any statistic data to share before and after this change?

[kreativityapps]

Before the fix I had a bunch of crashes with this:

java.lang.OutOfMemoryError: 
  at android.graphics.Bitmap.nativeCreate (Native Method)
  at android.graphics.Bitmap.createBitmap (Bitmap.java:1122)
  at android.graphics.Bitmap.createBitmap (Bitmap.java:952)
  at top.kikt.flutter_image_editor.core.ImageHandler.handleRotate (ImageHandler.java:29)
  at top.kikt.flutter_image_editor.core.ImageHandler.handle (ImageHandler.java:73)
  at top.kikt.flutter_image_editor.FlutterImageEditorPlugin.handle (FlutterImageEditorPlugin.java:17)
  at top.kikt.flutter_image_editor.FlutterImageEditorPlugin.access$handle (FlutterImageEditorPlugin.java)
  at top.kikt.flutter_image_editor.FlutterImageEditorPlugin$onMethodCall$$inlined$runOnBackground$1.run (FlutterImageEditorPlugin.java:55)
  at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1167)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:641)
  at java.lang.Thread.run (Thread.java:919)

The fix solved it, I will try to gather some memory measurements before-after when I have the time.

[kreativityapps]

I rotated several times the same image of size 4.5MB in my app.

Before:

• memory consumption goes up each time the image is rotated, above 400MB

After:

• memory consumption comes back after rotation, steady around 220MB

Thanks for this great package!

[AlexV525]

This look very promising! Thanks for the huge improvement.

[AlexV525]

Nit picking after merged: we recommend the minimum commit policy, which means this improvement should only including the native part as it scoped. But it's okay for now, can be improved in other PRs or projects.

[AlexV525]

Oops, sorry about forgetting to publish this. Will rush to it now.