Update to ImageSharp v4 Stable

[JimBobSquarePants]

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)

Description

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86%. Comparing base (620cbde) to head (47e39d9).

Additional details and impacted files

@@         Coverage Diff         @@
##           main   #399   +/-   ##
===================================
  Coverage    86%    86%           
===================================
  Files        83     83           
  Lines      2453   2453           
  Branches    366    366           
===================================
  Hits       2119   2119           
  Misses      223    223           
  Partials    111    111           

Flag	Coverage Δ
unittests	86% <ø> (ø)

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