initial support for special HEIF metadata

[bigcat88]

Read Only support for some part of data from this issue: #234

def test_pillow_read_heif_metadata():
    im = Image.open("images/heif_other/spatial_photo.heic")
    assert "heif" in im.info
    assert im.info["heif"]["camera_intrinsic_matrix"] == {
        "focal_length_x": 1525.444598197937,
        "focal_length_y": 1525.444598197937,
        "principal_point_x": 1280.0,
        "principal_point_y": 1280.0,
        "skew": 0.0,
    }
    assert im.info["heif"]["camera_extrinsic_matrix_rot"] == (1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0)

So far I've managed to do reading and only for two fields.

Although libehif added a low-level API for reading of everything?, it's still in beta, so this is the only way I've managed to do it for now.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (48a9760) to head (661d39d).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #271   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           10        10           
  Lines          936       952   +16     
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+ Hits           936       952   +16     

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