`Polygons` packing incorrectly trims textures inside mesh hulls

[misaki-eymard]

Description:
When Polygons packing is selected in the Texture Packer settings, texture regions inside a mesh hull may be incorrectly trimmed in the packed texture.

Expected behavior:
Texture regions inside a mesh hull should not be trimmed when Polygons packing is selected in the Texture Packer settings.

Steps to reproduce:

1. Download the attached .zip file: 1076-polygon-packing-trims-mesh-texture.zip
2. Open the Spine project included in the archive. The skeleton contains only one mesh attachment with a blue rectangular image:

3. Press Ctrl + E to open the Export window.
4. Select either JSON or binary export, then click the Pack Settings button.
5. In the Texture Packer settings, select Polygons packing:

6. Click OK, then export the skeleton.
7. Check the packed texture. The rectangle has been cut in half and incorrectly packed as a triangle:

Version where this issue was observed:
4.3.23

This issue was reported in the following forum thread:
https://esotericsoftware.com/forum/d/30519-problems-when-packing-rectangular-images-into-a-polygon-format