HaikuDepot: Icon / Tarball Handling

Instead of exploding the tar-ball of icons from
HDS, keep it as a tar-ball, index it and read
data directly out from specific indicies on demand.

This will speed up the process of downloading
the icons by removing the unpack. Also updates
will be faster by avoiding the need to delete the
old icon files.

Because icons are loaded on-demand, the start
time is faster by avoiding all the icon loads.
There are also savings on memory consumption.

Indexing on each load is surprisingly fast so
no external index is maintained. Likewise for
the tar-balls's meta-data.

This commit does not cover the implementation
of an LRU cache of the icons in memory.

Relates to #15370

Change-Id: Ia1647d8c805be89618f493d2592bf7877fca3f14
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3205
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

HaikuDepot: Featured Pkgs View

This change will move the display of the featured packages
from a dynamic layout to one that is static. This should
improve layout consistency and ui performance as well as
introduce keyboard navigation in the featured packages
list.

Resolves #11675, #15012
Helps #14675

Change-Id: Iddac7a9562763c7a890ec5dcf633e94f84684f43
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2708
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>