Fix Linebreak issues #443 and #444

[JimBobSquarePants]

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Description

Fixes #443 and #444
I realised during debugging of this issue that I was attacking the problem incorrectly. Instead of looping though the codepoints in the single line and attempting to match the correct line break, I identify the correct break by measuring the line at each one then slicing the textline once the correct break has been identified. This approach avoids back searching and additional complexity, ensuring that the correct break is always used.

Copilot reviewed 5 out of 12 changed files in this pull request and generated no comments.

Files not reviewed (7)

• tests/Images/ReferenceOutput/Issue_444_A__WrappingLength_860_.png: Language not supported
• tests/Images/ReferenceOutput/Issue_444_B__WrappingLength_860_.png: Language not supported
• tests/Images/ReferenceOutput/Issue_444_C__WrappingLength_860_.png: Language not supported
• tests/Images/ReferenceOutput/Issue_444_D__WrappingLength_860_.png: Language not supported
• tests/Images/ReferenceOutput/Issue_444_E__WrappingLength_860_.png: Language not supported
• tests/Images/ReferenceOutput/ShouldBreakIntoTwoLinesA__WrappingLength_1000_.png: Language not supported
• tests/Images/ReferenceOutput/ShouldBreakIntoTwoLinesB__WrappingLength_100_.png: Language not supported

Comments suppressed due to low confidence (3)

tests/SixLabors.Fonts.Tests/Issues/Issues_444.cs:10

• [nitpick] The variable name 'charisSL' is inconsistent with the font name 'CharisSIL'. It should be renamed to 'charisSIL'.

private FontFamily charisSL = new FontCollection().Add(TestFonts.CharisSILRegular);

src/SixLabors.Fonts/TextLayout.cs:1382

• The method signature of InsertAt was changed to void, but the return statement was not removed. This could lead to confusion.

RecalculateLineMetrics(this);

src/SixLabors.Fonts/TextLayout.cs:1353

• The variable graphemeIndex was renamed to graphemeCodePointIndex in one place but not consistently throughout the code. This could lead to confusion.

if (graphemeCodePointIndex == 0)

[jez9999]

charisSL variable should presumably be charisSIL.