Replace our type checker with a standard one

[gonzaponte]

For some reason, I went on a mission to write a type checker for IC (#824) instead of using one of the options already available in the community. These are surely, much better:

• enforce
• pydantic
• pytypes

I don't recall this having a good motivation, so we need to find some time to look into (at least some of) them and assess which is better suited for us.

Also somewhat related to #900.