Use getFTLPID instead of pidof

[yubiuser]

What does this PR aim to accomplish?:

Currently, we use pidof to test if FTL is running. However, there are hints that pidof might be a bit unreliable to find all processes. See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=926896 and https://unix.stackexchange.com/questions/518411/why-is-pidof-not-working

This as also been reported in one of our issues: #307 (comment)

How does this PR accomplish the above?:

1. Replacing pidof with getFTLPID, a function that we also use in core. It'll read the PID from pihole-FTL.pid file FTL writes on it's start.
2. Additionally, this PR adds the h option to the ps command for getting FTLs CPU and memory utilization to save one pipe to tail.

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[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[github-actions]

Conflicts have been resolved.

[yubiuser]

Added a small visual improvement.