Allow `LiveContract` creation from `FileId`s

[3Nigma]

Given an existing contract's bytecode hosted at a FileId, we should allow the deployment of a new LiveContract through that FileId.

This one is near and dear to @victorholo's heart. We just hope to get the API right.

[3Nigma]

The following working variants are considered:

• Contract.newFrom({ path: "0.0.X" }) and Contract.newFrom({ path: FileId.fromString("0.0.X") }
  • Note: the challenge here is that, since you need an ApiSession to retrieve the actual file content, that won't be immediately available on the Contract itself so we would end up deferring it.
• ApiSession.getLiveFile(id).asContract(abi = [], name = undefined) -- would add dependency to #119 . Or we can do a bodged version of it (similar to getLiveJson) or ... better yet ... start out the work on #119 in parallel and only provide the live-file variant of that respectful method.

In both of the above cases, when deploy-ing the contract to make it live, we would have to make sure to not double-create the File that the contract's bytecode depends on.