This patch simplifies the color handling logic in Editline and
IOHandlerEditline:
- Remove the m_color_prompts property from Editline and use the prompt
ANSI prefix and suffix as the single source of truth. This avoids
having to redraw the prompt unnecessarily, for example when colors
are enabled but the prompt prefix and suffix are empty.
- Rename m_color_prompts to just m_color in IOHandlerEditline and use
it to ensure consistency between colored prompts and colored
auto-suggestions. Some IOHandler explicitly turn off colors (such as
IOHandlerConfirm) and it doesn't really make sense to have one or the
other.
6ebbb1f536