feat: full mappo system integration test

[RuanJohn]

What?

Full distributed Jax mappo system integration test.

Why?

Part of on going efforts to increase testing code coverage of callback redesigned Mava.

Extra

closes #542 In order to be able to set lp_launch_type=lp.LaunchType.TEST_MULTI_THREADING we have to copy the node function here as well which is similar to what is done in the single process case.