Allow NodeJS cmd line options to be passed to NodeRED process

[hardillb]

fixes #571

Description

Allows the Node-RED max_old_space_size to be set rather than hard coded

Adds

• heapSize as device.yml config option
• -s or --heap-size cmd line arguments

Related Issue(s)

#571

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
• Link to Changelog Entry PR, or note why one is not needed.

Labels

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

[ppawlowski]

Shouldn't we drop this approach in favour of using NODE_OPTIONS environmental variable? IMO, this is a more universal solution.
Additionally, with this change, we will also have to update the system's service templates created by the Device Agent Installer.

[knolleary]

Don't think we should assign a short-alias for this.

Also need to resolve the feedback fro @ppawlowski - not sure the right approach.

Nick is now out on holiday for 10 days