fix: check for child process exits periodically

[XavierChanth]

fixes #1193

- What I did

• Created a dynamic array to track process ids for child processes created during the lifecycle of the program
• In between each monitor message read, check if each child process has exited (with waitpid) and remove it from the queue
• This solution assumes that 99% of the time there will be only 0 or 1 child process
  • 1% or less there will ever be 2 or more.

- How I did it

- How to verify it

- Description for the changelog
fix: check for child process exits periodically

[XavierChanth]

@cconstab can you test that this fixes your issues in #1193 please

[JeremyTubongbanua]

Quickly read over the code and LGTM