Add support decoding tiffs with horizontal predictor and bit depth > 8

[brianpopow]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
• I have provided test coverage for my change (where applicable)

Description

This PR adds support for decoding tiff's with horizontal predictor for 16/32 bit gray tiff's and 16/32 bit color tiff's.

[codecov]

Codecov Report

Merging #1729 (05a4c5e) into master (a6c708f) will increase coverage by 0.07%.
The diff coverage is 99.45%.

@@            Coverage Diff             @@
##           master    #1729      +/-   ##
==========================================
+ Coverage   84.43%   84.50%   +0.07%     
==========================================
  Files         833      833              
  Lines       36390    36565     +175     
  Branches     4257     4276      +19     
==========================================
+ Hits        30725    30899     +174     
  Misses       4845     4845              
- Partials      820      821       +1     

Flag	Coverage Δ
unittests	84.50% <99.45%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...rp/Formats/Tiff/Compression/HorizontalPredictor.cs	99.54% <99.41%> (-0.46%)	⬇️
...ompression/Decompressors/DeflateTiffCompression.cs	96.00% <100.00%> (+0.34%)	⬆️
...ff/Compression/Decompressors/LzwTiffCompression.cs	100.00% <100.00%> (ø)
...rmats/Tiff/Compression/TiffDecompressorsFactory.cs	71.42% <100.00%> (ø)
src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs	89.92% <100.00%> (+0.29%)	⬆️

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[JimBobSquarePants]

LGTM 👍