Opponent seed is not propagated after env.copy()

[BDonnot]

Environment

• Grid2op version: 1.6.4
• System: windows
• Additional system information: None

Bug description

When calling "env.copy()" the opponent does not attack correctly.

This is probably due to an issue in the "seed" function.

How to reproduce

Code snippet

import grid2op
env = grid2op.make("l2rpn_icaps_2021", test=True)
env.seed(3)
env.reset()
print(f"{env._opponent._attack_times = }")
env_cpy = env.copy()
print(f"{env._opponent._attack_times = }")
print(f"{env_cpy._opponent._attack_times = }")
... # Some code 

Current output

env._opponent._attack_times = array([  5, 105, 180])
env._opponent._attack_times = array([  5, 105, 180])
env_cpy._opponent._attack_times = array([], dtype=int32)

Expected output

env._opponent._attack_times = array([  5, 105, 180])
env._opponent._attack_times = array([  5, 105, 180])
env_cpy._opponent._attack_times = array([ 5, 105, 180], dtype=int32)