The set of application icons provided in the linux packaging is confusing and duplicated

While working on packaging the GUI for Arch Linux (see #10546) I got a bit confused by the icons in media/icons/Keybase.iconset/ (used by build_binaries.sh) since they seem to all be duplicated since there seems to be two copies of each one, and the extra copies are all the "wrong" size. Which include 64x64 and 1024x1024 which aren't otherwise there. What are these extra ones for, and why aren't 64/1024 sized icons installed if they exist?

Start by inspecting media/icons/Keybase.iconset/ and the icon handling in build_binaries.sh. Compare the duplicated files and their sizes, then trace which icons Linux packaging installs. Done means the purpose and intended installed set of the duplicate and 64x64/1024x1024 icons are established and the packaging behavior is made consistent.

Written by the indexing model from the issue text.