Revised & extended test coverage for Resize

[antonfirsov]

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 matches 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)

Issues addressed:

• There were no test cases for scale-up
• Resize_WorksWithAllResamplers was not covering all resamplers
• Resize was not tested for non-typical dimensions values

All new test cases were by changing/extending the input for Resize_WorksWithAllResamplers. We need these tests to implement #642 in a safe way.

Unrelated changes:

• TolerantMath.Default is a readonly field now
• Minor additions + code cleanup in test utilities

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@dce781d). Click here to learn what that means.
The diff coverage is 95.12%.

@@            Coverage Diff            @@
##             master     #782   +/-   ##
=========================================
  Coverage          ?   88.68%           
=========================================
  Files             ?     1012           
  Lines             ?    43306           
  Branches          ?     3185           
=========================================
  Hits              ?    38404           
  Misses            ?     4197           
  Partials          ?      705

Impacted Files	Coverage Δ
src/ImageSharp/Common/Helpers/TolerantMath.cs	100% <100%> (ø)
...ests/TestUtilities/Tests/TestImageProviderTests.cs	97.57% <100%> (ø)
...sing/Processors/Transforms/ResizeKernelMapTests.cs	83.59% <100%> (ø)
...estUtilities/ImageProviders/TestPatternProvider.cs	98.01% <100%> (ø)
...TestUtilities/Attributes/ImageDataAttributeBase.cs	81.66% <100%> (ø)
tests/ImageSharp.Tests/TestUtilities/TestUtils.cs	85% <88%> (ø)
...ts/Processing/Processors/Transforms/ResizeTests.cs	99.52% <97.77%> (ø)

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[antonfirsov]

This is worth to check (and cry).

[JimBobSquarePants]

Not worth us trying to fix it. NN is low quality anyway and 32bit NET Framework would be increasingly rare. I’d put a note and skip test on those platforms.