Make passing and returning Numbers from JS less annoying

[fl0rek]

Many of our APIs accept/return 64bit unsigned integers, which on JavaScript side are mapped to BigInts. This requires manual conversion: await node.get_header_by_height(BigInt(1)) rather than being able to use 1 literal. This is due to JS number being able to hold up to 53 bit integers without losing precision. We'd like to hide this detail and switch to API which allows passing both Numbers and BigInts.