Add Span params for CreateXXX in C#

[ODtian]

Currently, when the fixed-length array in the structure is initialized using Create, the parameter type is an array. This is not conducive to reducing GC overhead. Adding an interface that takes Span as a parameter is more friendly to 0GC programs.

[jtdavis777]

this sounds like a great feature to add -- is this the same construct as C++ spans? Would this change be backward compatible if we just updated the api instead of adding an additional one?

I would love to see a PR for this I think.