Support @coral-xyz/anchor 0.30

[intergalacticspacehighway]

Thanks for the library. I ran into an error on calling AmmImpl.create. Error: Cannot read property '_bn' of undefined. Found that it needs some work to support anchor 0.30.0. There had been some breaking changes in 0.30. I think biggest one is the change of program constructor. This changes how Program is constructed here.