Enumerate once on clone. Fix #1073

[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

We were allowing enumerating our source ImageFrame<TPixel> collection more than once on clone causing memory leaks so I've switched the code to explicitly enumerate once and pass an array to the new image constructor.

Fixes #1073

[JimBobSquarePants]

Best to call the method above to ensure no diversion is possible in future refactoring.

[codecov]

Codecov Report

Merging #1074 into master will decrease coverage by 0.12%.
The diff coverage is 91.66%.

@@            Coverage Diff             @@
##           master    #1074      +/-   ##
==========================================
- Coverage   89.95%   89.83%   -0.13%     
==========================================
  Files        1200     1200              
  Lines       53010    53013       +3     
  Branches     3844     3847       +3     
==========================================
- Hits        47687    47623      -64     
- Misses       4555     4562       +7     
- Partials      768      828      +60

Impacted Files	Coverage Δ
src/ImageSharp/ImageFrameCollection.cs	90% <0%> (ø)	⬆️
src/ImageSharp/Image{TPixel}.cs	90% <100%> (+0.34%)	⬆️
...essing/Processors/CloningImageProcessor{TPixel}.cs	90.38% <100%> (+0.18%)	⬆️
...c/ImageSharp/Formats/Tga/TgaImageTypeExtensions.cs	60% <0%> (-20%)	⬇️
...xelFormats/PixelOperations{TPixel}.PixelBenders.cs	89.9% <0%> (-10.1%)	⬇️
...olorSpaces/Conversion/ColorSpaceConverter.Adapt.cs	60% <0%> (-8.58%)	⬇️
...Processing/Processors/Transforms/TransformUtils.cs	87.64% <0%> (-6.75%)	⬇️
src/ImageSharp/Primitives/ValueSize.cs	78.94% <0%> (-5.27%)	⬇️
src/ImageSharp/Common/Helpers/ImageMaths.cs	82.5% <0%> (-5%)	⬇️
....Tests/TestUtilities/Tests/TestEnvironmentTests.cs	63.63% <0%> (-4.55%)	⬇️
... and 26 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update dadc274...5b7052c. Read the comment docs.

[JimBobSquarePants]

I'm just gonna go ahead an merge this one. It's a trivial and obvious fix.