UBUNTU: [Packaging] use default zstd compression

UBUNTU: [Packaging] use default zstd compression

Revert "UBUNTU: [Packaging] enforce xz compression for debs"

This reverts commit 45da4d72dea537910d970211ff8c345f4f9a2775.

The previous commit incorrectly stated that jammy dpkg default has
switched from xz to zstd. This change was done late in impish
cycle. [1] It also incorrectly states that there are no evident benefits
for the kernel packages to use zstd.

It is correct that zstd compression may require more
resources. However, the decompression speed and decompression memory
requirements are a lot faster. The choice to switch from xz to zstd by
default in Ubuntu was done to speed up installation and upgrade of all
packages, at the expense of slightly larger download sizes.

If we do want to futher optimize compression methods it should
probably be done on per subpackage type. For example, linux-image-ABI
already contains compressed kernel image and not much else, we can
choose to not compress that deb at all with compression method
none. Debug symbols are usually rarely installed, thus it might make
sense to keep them small and thus choose compress ddebs with
xz. However modules and tools should remain compressed with zstd.

[1] https://launchpad.net/ubuntu/+source/dpkg/1.20.9ubuntu2

Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>