feat: Add possibility to create custom Network Policies for project pods

[ppawlowski]

Description

This PR introduces a feature which allows to configure custom Kubernetes Network Policies for NodeRed instances.
Additionally, it removes hardcoded and unused Network Policy.

Related Issue(s)

#322

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production

Labels

• Backport needed? -> add the backport label
• Includes a DB migration? -> add the area:migration label

[ppawlowski]

The Helm chart validation is failing because during the upgrade process from the previous chart version to the current one, the --reuse-values flag is used. As a result, new default values shipped with the new chart version are ignored.
This issue has been already reported and some PR was already introduced.
However, until the chart-testing tool will not provide a possibility to configure the mentioned helm command parameter, there is a need to implement a workaround by validating all new chart values. The simplest way to achieve this is described here.