Motivation
We want to be able to run the test suite from EF

Description
This is a first implementation that adds support to parse a simple test vector with one block and one transaction.

Pending work:

• Add a script to download all test vectors, and filter out ones previous to Cancun.
• Extend ef_tests types to succesfully parse all cancun blockchain tests.
• Add logic to skip tests that are not supported yet.
• Call EVM inside core instead of the one inside ef_tests once it's ready. This will require to use types from core and be able to go from ef_tests into core types.

Closes #43