Using int was a mistake. This patch changes String, StringImpl,
StringView and StringBuilder to use size_t instead of int for lengths.
Obviously a lot of code needs to change as a result of this.
Get rid of the dedicated Emoji class to make it easier to store a null
value signifying a failed lookup.
This allows us to remember failed lookups, making subsequent failures
for the same codepoint much faster. :^)
Instead of LibGUI and WindowServer building their own copies of the drawing
and graphics code, let's it in a separate LibDraw library.
This avoids building the code twice, and will encourage better separation
of concerns. :^)
