Draft: destroy sparsity maps in deppart test
This PR is a result of "profiling" with sparsity map ref-counting on that showed we are leaking sparsity maps in deppart test:
PR adds IndexSpace<>.destroy() on all index spaces in all tests before runtime shutdown. Practically speaking this change is not required for this test work (and be correct) but is desired to make the recycling of the sparsity maps explicit.
Edited by apryakhin