Cleanup precompile configuration & setup

[darioush]

The chain config, genesis, and precompiles have become intertwined, which makes setting up unit tests and mocking difficult.
For example, in a more ideal setup unit tests can set up precompiles that have one or all of:

• contract address + code to run,
• Predicater interface
• Accepter interface

within a few lines of setup. This PR at this commit shows an example of the current situation which is not ideal.