Create associated token account idempotent instruction

[lucasoares]

Currently solana-go only allows creating non-idempotent instruction for the associatedtokenaccount.NewCreateInstructionBuilder program instruction.

It would be nice to allow it to be created using the idempotent solution, which is achieved by having a [1] uint8 bytearray as the instruction data.

I do not understand the gagliardetto/binary library's internals and don't know how the BaseVariant works. The current binary module doesn't have much documentation, but if you guide me it appears to be an easy PR.

Loved the work you have done with this library. I will be using it a lot for personal projects, and I want to know more about it to contribute. Thanks!