feat(linux): port transactional installer upgrade mode and in-app updater - #360

'Letter.GlyphRectangle' is obsolete: 'Use BoundingBox instead.'

'Bitmap.Save(string, int?)' is obsolete: 'Use the overload accepting BitmapEncoderOptions instead.'

Nullable value type may be null.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Possible null reference argument for parameter 'collection' in 'void Assert.Contains<string>(string expected, IEnumerable<string> collection)'.

'IPdfImage.Bounds' is obsolete: 'Use BoundingBox instead.'