Clean up tmpfiles snippet

• Remove entries for passwd and friends, these will already be populated by systemd-sysusers before tmpfiles has a chance to run so these entries don't actually do anything.
• Remove entries for files that only have comments in them. These files only end up cluttering /etc making it harder to figure out what's local admin configuration at a glance.
• Symlink all other files that actually do something instead of copying them. By copying them, we will never receive any updates if the files are updated in /usr/share/factory/etc as tmpfiles will only copy the files if they don't exist in /etc already. By symlinking instead of copying, any updates to /usr/share/factory/etc will automatically be taken into account.

tmpfiles

-# copy from factory when missing
+# Symlink from factory when missing
 
-C /etc/arch-release
-C /etc/crypttab
-C /etc/fstab
-C /etc/group
-C /etc/gshadow
-C /etc/host.conf
-C /etc/hosts
-C /etc/issue
-C /etc/ld.so.conf
-C /etc/nsswitch.conf
-C /etc/passwd
-C /etc/profile
-C /etc/profile.d/locale.sh
-C /etc/securetty
-C /etc/shadow
-C /etc/shells
-C /etc/subuid
-C /etc/subgid
+L /etc/arch-release
+L /etc/host.conf
+L /etc/issue
+L /etc/ld.so.conf
+L /etc/nsswitch.conf
+L /etc/profile
+L /etc/profile.d/locale.sh
+L /etc/securetty
+L /etc/shells