With a little help (read: copy & paste) from ImageWidget, QuickShow will
now cycle through the frames of animated images - enjoy the cat GIFs!
Future improvement: cache decoded images like LibWeb's ImageResource to
waste less CPU - the same applies to LibGUI though, maybe we can put
something shared in LibGfx.
Closes#5837.
Now the pixel under the cursor doesn't move, which is more consistent
with other image viewers (e.g. GwenView and IrfanView). Also switch
m_pan_origin to use window space to have less space transformations.
This is basically just for consistency, it's quite strange to see
multiple AK container types next to each other, some with and some
without the namespace prefix - we're 'using AK::Foo;' a lot and should
leverage that. :^)
