CPU consumption is not reflected correctly in the system monitor of debug panel

[cuileri]

Tribler version/branch+revision:

7.0.0-GIT

Operating system and version:

Ubuntu 18.04.2 LTS

Steps to reproduce the behavior:

Open debug window's System/CPU tab and OS's system monitor at the same time

Expected behavior:

Debug panel's System/CPU tab shows actual CPU usage of all subprocesses related to Tribler

Actual behavior:

Debug panel's System/CPU tab shows missing information on Tribler's CPU usage. It only reports the main process.

Relevant log file output:

[xoriole]

It seems the matplotlib trust graph creates a separate process instead of running within the core process and this new process is consuming high cpu. If Trust graph is not enabled, there is no such process. We should investigate more on this to make it efficient.