Remove requirement to compile SDK testing utils with ABI generation

[austinabell]

This issue could just as easily be opened in the SDK repo, but since it's more relevant to this I'm opening it here.

Roughly the pattern that would be easiest would be:

• Add testing feature to SDK, which gates the nearcore dependencies behind it and makes it default (has benefits to SDK)
• Modify crate toml to use the same version of the SDK but with no default features and "abi" feature (there will also have to be parsing to include other features like "unstable" that might be included). This also would have the benefit of not requiring the developer to enable abi feature on their crate by default

Maybe this is janky, is there a better way?