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.netname/rootfs/etc/systemd/network/10-ww4-netname.link.ww

@@ -1,5 +1,5 @@
 {{ range $devname, $netdev := .NetDevs -}}
-{{ file (print "10-ww4-netname-" $devname ".link") }}
+{{- file (print "10-ww4-netname-" $devname ".link") -}}
 # This file is autogenerated by warewulf
 {{- if and $netdev.Hwaddr $netdev.Device }}
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