Fabric module refactor

[booky10]

Breaking changes

• Nearly all packetevents fabric internals have been changed

Changes

• Splits sources into client and common sources to prevent accidentally using client code
• Sets up a PacketEvents api instance on both the client and server
• Simplifies network pipeline injection and encoder/decoder handling
• Uses proper SLF4J logger instead of System.out
• Uses fabric access wideners for accessing player connection internals instead of reflection
• Fixes PacketEvents Fabric Client issue #1025

Todo

• Look at other platforms and search for stuff which could be missing
  • Associate platform player instance with connection channel
• Testing on client and dedicated server
• Find a way to create packetevents instances for singleplayer worlds (internal server; maybe using events other mods could listen to?)
  • Not possible without loading packetevents on an additional, separate classpath or removing usage of the static instance (which is used everywhere...)

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Closes #1026
Closes #1027

[Bram1903]

@booky10 once again a great PR! Looks really good! Now I can add support for Fabric to my AntiHealthIndicator!

[Axionize]

I've worked with Booky to ensure this works. Can we please merge this into upstream so I don't have to maintain this upstream fork and have everyone who contributes to my project build packevents just to build my project?