Test for CODECOPY'ing initialization code

[OlivierBBB]

We need a test for CODECOPY'ing initialization code. This is in the wake of realizing that account snapshots weren't working properly, see commit b9d0c4a.

Example initialization code

CODESIZE
PUSH1 0x00
PUSH1 0x00
CODECOPY

// we could stop here
// what follows is just
// a means to visualize
// the CODECOPY operation

PUSH1 0x00
MLOAD

// again, we could stop
// here on an empty code
// deployment

CODESIZE
PUSH1 0x00
RETURN

We finish on a RETURN instruction that deploys the initialization code but we may as well