This is a minimal set of changes to make things work with the new types
in nim-eth - this is the minimal PR that merely resolves
incompatibilities while the full change set would include more cleanup
and migration.
1. test_state_db and test_ledger -> test_ledger.
They are the same thing now.
2. stack, memory, code_stream, gas_meter, misc,
overflow -> test_evm_support.
They are small tests and fall into the same area.