miscellaneous optimizations (optimizing at 3am is addicting)

[LukynkaCZE]

I did lot of profiling and addressed some of the most performance heavy stuff

• Add ObjectPool and make Inflater and Deflater in NetworkCompression pooled to reduce overhead of creating those objects for every tcp frame
• Optimize reading and writing VarInts
• Make properties of EventContext lazy since they are rarely accessed anyway and combining sets is expensive
• Make schematic placing use fastutil maps and sets
• Don't construct packets for sidebar, bossbar and hologram updates if there are no viewers

There's still more to be addressed at some other point:

• Consider moving to Native C implementation of cipher (for encryption) and zlib (for compression) like in velocity
• Look into optimizing string operations in Scroll
• Look into optimizing string operations in Block#parseBlockStateString
• Packets are written by Dockyard in a Netty IO Event Loop thread #179 (this also causes the netty thread to block which could cause tiny lag spikes)