Automatically Generate `autorm` Scripts to Properly Handle Purging Behaviors

[ZeroAurora]

Currently, most packages don't have autorm script populated in AOSC. This don't match the behavior of common dpkg distributions like Debian, where build scripts will generate post-removal scripts for maintainance.

One example is that in common dpkg distributions, dh_installdebconf will automatically insert debconf db_purge commands for packages having config to purge the debconf database when a package is purged. In AOSC we don't have this behavior, causing incomplete configuration cleaning when, for example, oma purge.

This is an example from an existing Debian installation:

# Automatically added by dh_installdebconf/13.24.1
if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
	. /usr/share/debconf/confmodule
	db_purge
fi
# End automatically added section

Same as above, many other debhelper scripts insert corresponding purging behaviors in package building process. AOSC doesn't use debhelper and build process is done in autobuild, so this should be handled properly.