Completely rewrite Code mobject + add support for short notation RGB(A) hex code specifications to ManimColor (#4115)

Co-authored-by: Francisco Manríquez Novoa <49853152+chopan050@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people