Charts[Network Node]: Standardize names of all named partial template files by prefixing the name with an underscore

## User Story

_**As a Helm chart developer,**_

**I want**

> to be assured the chart partial templates are not accidentally rendered as manifest outputs.

**So that**

> I can avoid erroneous and hard to debug issues.


## Requested Changes

- Ensure each and every partial template file ends with a `.tpl` extension and begins with an underscore (`_`).
