Use FTL's API endpoint to get Pi-hole's status

[yubiuser]

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What does this PR aim to accomplish?:
Instead of using pihole status web to get the Pi-hole status, use the native FTL API endpoints >stats and >dns-port (pi-hole/FTL#1264) to determine Pi-hole's current status.
Drawback of pihole status web is that it needs sudo powers to run the function. Calling the endpoints directly does not require elevated privileges.

The logic is now the following (mimicy of pihole status web): If no FTL PID is found or the DNS part if Pi-hole is disabled, the status is "DNS offline". If this is not the case, everything depends on status returned by >stats. It can either be "enabled", "disabled" (blocking off) or "unknown".