Enable more mkosi options

- HostonlyInitrd reduces the size of the initramfs which speeds up
QEMU boot times.
- Autologin and deleting the root password remove
the manual login step whenever starting the systemd-nspawn container
or QEMU vm.
- NetworkVeth passes --network-veth to the nspawn container when
using mkosi boot and emulates --network-veth with a tap device
and networkd's 80-vm-vt.network builtin network file when using
mkosi qemu. --network-veth makes it easier to test network and
resolved in mkosi's nspawn container or QEMU vm.

.mkosi/mkosi.arch

@@ -63,3 +63,8 @@ Packages=
 
 [Host]
 QemuHeadless=yes
+NetworkVeth=yes
+
+[Validation]
+Password=
+Autologin=yes

.mkosi/mkosi.debian

@@ -79,3 +79,8 @@ Packages=
 
 [Host]
 QemuHeadless=yes
+NetworkVeth=yes
+
+[Validation]
+Password=
+Autologin=yes

.mkosi/mkosi.fedora

@@ -89,3 +89,8 @@ Cache=mkosi.cache
 
 [Host]
 QemuHeadless=yes
+NetworkVeth=yes
+
+[Validation]
+Password=
+Autologin=yes

.mkosi/mkosi.opensuse

@@ -83,3 +83,8 @@ Packages=
 
 [Host]
 QemuHeadless=yes
+NetworkVeth=yes
+
+[Validation]
+Password=
+Autologin=yes

.mkosi/mkosi.ubuntu

@@ -82,3 +82,8 @@ Packages=
 
 [Host]
 QemuHeadless=yes
+NetworkVeth=yes
+
+[Validation]
+Password=
+Autologin=yes