[feature][BTIP-55]: Change the centralized challenge to be more decentralized

[Shawn-Huang-Tron]

Currently, the host that stored the file from the renter would receive a challenge from the official to prove that they didn't lose the file. However, the process is centralized.
Now we hope this process is decentralized and that would be awesome.

[simbadMarino]

This is a great step going fordward! Is this role planned to be an automated rol within the network or node owners will have the flexibility to chose their role at discretion?