Implement the Ryu Printf algorithm

[HertzDevil]

This is a direct port of d2fixed.c. See #8441 (comment). Note that Dragonbox does not have an equivalent for arbitrary precision printing.

sprintf does not use this yet, because currently the algorithm can only write to a buffer, never to an IO. On the other hand Number#format can probably switch to this method immediately.

[straight-shoota]

You named this as an alternative approach to #13143.
What's missing here?

[HertzDevil]

String::Formatter#float needs to be patched to use Ryu Printf rather than LibC.snprintf, and then Crystal::System.print_error can use String#% directly.

For LibC.printf: #13161