Tests for alignment should be added

[stephenswat]

Also following #181, we need to add new tests to ensure that the alignment requirements are actually met. Preferably after #183 is completed.

[krasznaa]

Was done a while ago with:

• https://github.com/acts-project/vecmem/blob/main/tests/common/memory_resource_test_alignment.ipp
• https://github.com/acts-project/vecmem/blob/main/tests/core/test_core_memory_resources.cpp#L123-L131

Though we may want to still do a little bit more for the "device resources". 🤔 With those only the SYCL memory resources align their allocations explicitly. With CUDA and HIP we get a 0x400 alignment on all allocations, which tends to be enough in real life. Though would fail the alignment tests shown above. 🤔