debian: Initial packaging for re-introduction

This commit re-introduces 'kvmtool' to Debian archives. It was previously
removed in 2022 due to lack of maintenance (RoQA), but it remains a useful
tool for architecture development and kernel testing.

Major changes and modernization:
- Switch to debhelper-compat (= 13) in debian/control.
- Update Standards-Version to 4.7.0.
- debian/control:
  * Update Build-Depends: add libfdt-dev, libaio-dev, xorriso.
  * Set Architecture to 'linux-any' to support RISC-V and others.
  * Update Maintainer information.

Signed-off-by: Yunseong Kim <ysk@kzalloc.com>

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Date:      Sun Nov 23 06:52:08 2025 +0000
#
# On branch debian/latest
# Changes to be committed:
#	new file:   debian/changelog
#	new file:   debian/control
#	new file:   debian/copyright
#	new file:   debian/kvmtool.manpages
#	new file:   debian/patches/0001-builtin-run-Fix-warning-when-resolving-path.patch
#	new file:   debian/patches/0002-builtin-run-Replace-strncpy-calls-with-strlcpy.patch
#	new file:   debian/patches/0003-virtio-use-strlcpy.patch
#	new file:   debian/patches/0004-virtio-blk-Avoid-taking-pointer-to-packed-struct.patch
#	new file:   debian/patches/0005-net-dhcp-avoid-misleading-strncpy.patch
#	new file:   debian/patches/0006-kvmtool-9p-fix-overapping-snprintf.patch
#	new file:   debian/patches/series
#	new file:   debian/rules
#	new file:   debian/source/format
#
# Untracked files:
#	debian/files
#
