[Feature] Create minimal leo testing scaffolding

[vicsn]

🚀 Feature

For me personally, the scaffolding in this repository was very useful for locally testing behaviour of my leo program: https://github.com/AleoNet/aleo-multisig/tree/main/tests

It could be nice to extract some of the functionality and turn it into SDK utilities, as the SDK already committed to supporting leo devnode wrapping: https://github.com/ProvableHQ/sdk/tree/mainnet/create-leo-app/template-devnode-js

As an aside: in the past there were discussions about very advanced testing functionality mirroring https://github.com/venture23-aleo/doko-js - but that is a lot more work and is out of scope as far as this issue is concerned.

[iamalwaysuncomfortable]

@vicsn this is an existing formal epic for the SDK. The plan is to add functionality into create-leo-app that allows users to select a specific app config (node.js, web app, etc.) and be receive an out-of-box app config including tests.

This would involve the following:

• Generating contracts and tests via the ABI exported by the LEO CLI
• Either downloading the Leo CLI to build contracts or exporting it to wasm in order to build Leo contracts into Aleo contracts + the associated ABI and build an JS contract & test suite around it.