Implements InlineArrays which allow us to use Flatbuffers arrays within
Structs natively, and also implements FlatbufferVectors as a secondary API
when using mutable Structs
Fixes mutations within fixed sizes arrays
Adds tests and remove inout and mutating from generated objects in favor of borrowing
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Co-authored-by: Wouter van Oortmerssen <aardappel@gmail.com>