Peak memory usage for parallel tests

[noamgot]

Feature Request

When running the memray plugin over multiple tests in parallel (using pytest-xdist), it shows only the N tests that used most memory.

While that's great, I would like to see a summary of the total memory used by all tests together (especially I'd like to know what's the peak memory usage).

A possible solution might be using the vanilla memray, but I'm not sure how to do that, and regardless of that - I think it's useful to show this information in addition to the existing one.

Thanks!