Add test case for OpCode list equivalence

For now, we only test that we don't define extra opcodes in the
Haskell code; once we have parity, we can enable the (for now)
commented-out lines that check the reverse.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Agata Murawska <agatamurawska@google.com>