opensuse: prevent zypper from pulling busybox in the initrd

zypper's internal logic selects busybox-package variants of packages that are
required via dependency and not explicitly listed to install, which also causes
busybox to be added to the initrd.

Also, remove the shadow package (the equivalent to the shadow-utils package in
Fedora).

mkosi/resources/mkosi-initrd/mkosi.conf.d/10-opensuse.conf

@@ -7,6 +7,14 @@ Distribution=opensuse
 Packages=
         patterns-base-minimal_base
 
+        # Various packages added as dependencies. If they are not explicitly installed, the zypper inner
+        # logic picks the busybox-package variant, which adds also busybox in the initrd.
+        diffutils
+        grep
+        gzip
+        which
+        xz
+
         # Various libraries that are dlopen'ed by systemd
         libfido2-1
         libtss2-esys0
@@ -24,6 +32,10 @@ Packages=
 
         util-linux
 
+RemovePackages=
+        # Various packages pull in shadow to create users, we can remove it afterwards
+        shadow
+
 RemoveFiles=
         /usr/share/locale/*
         /usr/etc/services