Fix: Memory leak in ICUParagraphLayout::NextLine() (#11895)

This function calls icu::BreakIterator::createLineInstance() but does not clean up after it.

Instead use a static instance that is cloned (for thread-safety) and deleted as necessary.

(cherry picked from commit 6d276698b6)

src/gfx_layout.h

@@ -183,6 +183,7 @@ public:
 	Point GetCharPosition(std::string_view::const_iterator ch) const;
 	ptrdiff_t GetCharAtPosition(int x, size_t line_index) const;
 
+	static void Initialize();
 	static void ResetFontCache(FontSize size);
 	static void ResetLineCache();
 	static void ReduceLineCache();