Desktop: add plugin resources monitor

[DarkFalc0n]

This pull request is concerned with incremental development of the plugin resources monitor feature.

Summary:

• Added functions to get App Metrics from the electron API and add them to a map using the PID as key.
• Added OS Process ID in the Plugin object to identify respective metrics later while displaying.
• Added a polling function to repeatedly update metrics every 5 seconds (optimisation is WIP)

Testing:

• Manually tested through logging resourceMetric object and comparing it with top command output in linux.