Record a replay mod file

[TestingPlant]

We should implement a server plugin to record a replay mod file, especially once #912 is implemented. This will be helpful for content creators to make a video about the event.

[TestingPlant]

I've looked through the replay mod recording format and it seems trivial to implement. It is a zip file containing:

• some metadata files
• a recording.tmpcr file

The recording.tmpcr file appears to be all s2c packets, including the login success packet, concatenated together with some modifications:

• packets are never compressed
• packet length is encoded as a fixed-length big endian u32
• the time elapsed since joining is encoded as a big endian u32 and placed before the packet length. The time seemd to be measured somewhere between 1/1000 and 1/1024 of a second, but I can't seem to find an exact number.

I believe the best way to implement this feature would be to write a custom client which logs all s2c packets to place them into the recording.tmpcr file. The client would log in with a special username which tells the server to make the player vanished and tells the server to tell the proxies to send the player every broadcast local and subscribe the packet to all channels.