Move storage slots to the *-abi.json

[luizstacio]

In the past, we created storage slots JSON to keep the ABI clean of data specific to deployment. However, the storage slots were not a "required" file to initialize variables at deployment time.

Once we moved to "require" the storage slots, it reduced the ergonomic and required SDKs to check if a file exists and import automatically or ask the user to import it also. When dealing with deployment on browser envs, the work turns a bit worse and adds more steps to the final developer.

This problem is solved in the TS-SDK and RS-SDK, and the purpose here is to improve the abi. This isn't a blocker. It's just an improvement on DevEx.

Notes:

• Is this a valid work? If no, why we should keep it as it is?
• TS-SDK and RS-SDK are aware of the request, and the effort to implement it would be ok. They also agree this would be a good improvement.

Other potential features to be created:

• With the storage slots inside the abi, we could also consider adding types for the initialized slots.