Fix newline handling in file, softlink, and ImportLink template functions

Use state-based routing instead of sentinel strings, so whitespace-trimming
syntax (e.g. `{{- file "name" -}}`) correctly creates all named files and
symlinks.

Fixes: #2118

Signed-off-by: Jonathon Anderson <janderson@ciq.com>
Co-authored-by: Christian Goll <cgoll@suse.com>
Signed-off-by: Jonathon Anderson <janderson@ciq.com>

overlays/systemd.networkd/rootfs/etc/systemd/network/default.network.ww

@@ -1,5 +1,5 @@
 {{- range $devname, $netdev := .ThisNode.NetDevs }}
-{{ file (print "10-ww4-networkd-" $devname  ".network") }}
+{{- file (print "10-ww4-networkd-" $devname  ".network") -}}
 # This file is autogenerated by warewulf
 [Match]
 {{- if $netdev.Device }}