Unit Tests & New Natural Sort (#941)

* Added a lot of tests

* More tests! Added a Parser.NormalizePath to normalize all paths within Kavita.

* Fixed a bug where MarkChaptersAsUnread implementation wasn't consistent between different files and lead to extra row generation for no reason.

* Added more unit tests

* Found a better implementation for Natural Sorting. Added tests and validate it works. Next commit will swap out natural Sort for new Extension.

* Replaced NaturalSortComparer with OrderByNatural.

* Drastically simplified and sped up FindFirstEntry for finding cover images in archives

* Initial fix for a epub bug where metadata defines key as absolute path but document uses a relative path. We now have a hack to correct for the epub.

API.Tests/Comparers/ChapterSortComparerZeroFirstTests.cs

@@ -0,0 +1,17 @@
+using System.Linq;
+using API.Comparators;
+using Xunit;
+
+namespace API.Tests.Comparers;
+
+public class ChapterSortComparerZeroFirstTests
+{
+    [Theory]
+    [InlineData(new[] {1, 2, 0}, new[] {0, 1, 2,})]
+    [InlineData(new[] {3, 1, 2}, new[] {1, 2, 3})]
+    [InlineData(new[] {1, 0, 0}, new[] {0, 0, 1})]
+    public void ChapterSortComparerZeroFirstTest(int[] input, int[] expected)
+    {
+        Assert.Equal(expected, input.OrderBy(f => f, new ChapterSortComparerZeroFirst()).ToArray());
+    }
+}