Charts[Network Node]: Move the network node helpers file to the root template directory and rename to the standard helper file name

[nathanklick]

Description

The helpers/_network-node-helpers.tpl file into the root of the templates directory and rename the file to _helpers.tpl.

[leninmehedy]

Taking this ticket since I need to update _helpers.tpl as part of other tickets I have, i.e. #206