Reduce verbosity of @pytest.mark.limit_memory on failure

[tekumara]

Feature Request

When limit_memory fails it outputs a long list of allocations (in my case 56k lines of allocations!)
Being able to disable this, or show a very abbreviated summary, would be much more useful, eg:

Expected 10MB but got 20MB in allocations

[tekumara]

PS: Thank you for an awesome utility!