Optimize Bootstrap to pre build faster by using multiple threads

[aikar]

Divide up the work into multiple queues, and send those tasks back into the executor.

This lets us precache everything concurrently, reducing precache time by about 75%~ on a typical 8 core system.

Bootstrap time was seen taking up to 30 seconds of time in testing, which is long enough in Minecraft that data conversions may need to occur.

This brought it down to about 6-7 seconds.

[aikar]

Comparison: Before: After:

[RainWarrior]

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