Support graphics in konsole

As per https://invent.kde.org/utilities/konsole/-/merge_requests/594 konsole has support for sixel, iTerm2, and a subset of kitty.

• Support sixel
• Support iTerm2

Request fixes in konsole:

• OSC 4 for ANSI colors
• XTVERSION to detect iTerm2
• Fix DECSDM
• Sixel: text should overwrite image
• iTerm2: text should overwrite image
• Consume Privacy Message