classes/package: Add extended packaged data

classes/package: Add extended packaged data

Adds extended package data which is encoded as JSON which allows it to
encode more structure than the "flat" package data files. The extended
data might be much larger than the standard package data, so it is not
read by default and instead requires
oe.packagedata.read_subpkgdata_extended() to be called

Currently, the file sizes and ELF debug sources are saved off into the
extended package data

(cherry picked from commit db9cf430e54ae68da80fbc3fba80ce88d8df164d)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Reviewed-by: Saul Wold <saul.wold@windriver.com>
Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>