Passing image_orientation value to libheif

[bigcat88]

Changes concern only image encoding

Changes proposed in this pull request:

• Removed rotation of image before encoding.
• We add a parameter in the C module "image_orientation" that passes the orientation of the image to the libheif that should be recorded.

Orientation is taken from the same place(EXIF or XMP), so it should not be a big breaking change, in most(all?) cases results should be the same.

[codecov]

Codecov Report

Merging #168 (e77c4a0) into master (4614b8e) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #168   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           10        10           
  Lines          874       881    +7     
=========================================
+ Hits           874       881    +7     

Files	Coverage Δ
pillow_heif/as_plugin.py	100.00% <100.00%> (ø)
pillow_heif/heif.py	100.00% <100.00%> (ø)
pillow_heif/misc.py	100.00% <100.00%> (ø)