* ! Reimplement SharedArrayPool because it is internal in .net runtime
* ! Expose PublicArrayPool that maps to our copy of SharedArrayPool
* ! CodeGenerator that remaps System.Buffers.ArrayPool.Shared calls to Sandbox.PublicArrayPool
* ! Don't run ArrayPoolUpgrader in full engine builds
* ! Add tests that verifies ArrayPool.Shared replacements
* ! Remove ArrayPool.Shared from whitelist
* ! Build AST from nodes instead of parsing text
* ! Use Reflection to grab Gen2GcCallback instead of event polling
