loaders: getContract returns non-nullable ContractResult

[shazow]

Made ContractResult non-nullable (and renamed to be similar to AutoloadResult).

This way we can do more ergonomic

const { abi, name, ok } = await loader.getContract(address);
if (!ok) throw "failed"; // If we care, or skip this altogether if we don't
...

Rather than

const result = await loader.getContract(address);
if (result === null) throw "failed"; // Need this check either way, because it's nullable
const { abi, name } = result;
...

@SonOfMosiah what do you think?

[SonOfMosiah]

Looks great! I was thinking of a status or success variable and I ok does the trick.

[shazow]

I figure ok is a little closer to the Result-type that some other languages have. 🤷