LibWeb: Break lines until we have enough space between floats

Before this change, we'd always insert one line box fragment, even when
a float was taking up too much space on the line, and the fragment
didn't actually fit.

We now perform line breaks until we have enough space between floats.
This fixes many page layouts where we'd previously see small fragments
of inline content outside the right edge of the containing block.

Userland/Libraries/LibWeb/Layout/InlineFormattingContext.h

@@ -29,6 +29,7 @@ public:
 
     float leftmost_x_offset_at(float y) const;
     float available_space_for_line(float y) const;
+    bool any_floats_intrude_at_y(float y) const;
 
     float effective_containing_block_width() const { return m_effective_containing_block_width; }