Call Kokkos::initialize/finalize in UnitTestMain

[maartenarnst]

Currently, in the tests, Kokkos is initialised and finalised in each test body.

In

• Add View of Views debugging tool #267

@dalg24 suggested that we move Kokkos::initialize/finalize to UnitTestMain.cpp.

I've tried to do this. I've moved the Kokkos::initialize/finalize to UnitTestMain.cpp and then removed it everywhere from the tests (not only the new one in #267, but all tests).

The issue is then that some of the tools print to std::cout as part of their finalize callback. And so when we move Kokkos::finalize to main, hence after the conclusion of the test body, the test can no longer check this output. This leads to failure in test_space_time_stack_demangling.

I'm not sure how to solve it best. For "space time stack", we can move the printing functionality from the destructor of State to a print function. But then it wouldn't be clear how to call this function. An option may be to make State a singleton.