Unit testing for Sparse matrix class

[adhamsi]

Description

Implements unit testing for Sparse.cpp.

Closes #280

Proposed changes

Tests implemented:

• constructor
• setting data pointers
• setting values pointer
• copying values
• copying values, then attempting to set data/values (must result in error)
• allocating and destroying memory

Checklist

Put an x in the boxes that apply. You can also fill these out after creating
the PR. If you're unsure about any of them, don't hesitate to ask. We're here
to help! This is simply a reminder of what we are going to look for before
merging your code.

• All tests pass. Code tested on
  • CPU backend
  • CUDA backend
  • HIP backend
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows Re::Solve style guidelines.
• There are unit tests for the new code.
• The new code is documented.
• The feature branch is rebased with respect to the target branch.

Further comments

[shakedregev]

Tests are spuriously passing on Frontier (likely due to some pointer comparison that happens to be true). They are failing on CUDA, almost certainly because of the code I pointed out (and other places where it's repeated).

[pelesh]

This is a good start but requires some more work. Setting this as a draft.

[pelesh]

There is a minor warning that needs fixing:

In file included from /.../src/resolve/resolve/tests/unit/matrix/runSparseTests.cpp:8:
/.../src/resolve/resolve/tests/unit/matrix/SparseTests.hpp:186:40: warning: variable 'h_val_data' is uninitialized when used here [-Wuninitialized]
  186 |             mem_.copyArrayDeviceToHost(h_val_data, A->getValues(memory::DEVICE), nnz);
      |                                        ^~~~~~~~~~
/.../src/resolve/resolve/tests/unit/matrix/SparseTests.hpp:182:32: note: initialize the variable 'h_val_data' to silence this warning
  182 |           real_type* h_val_data;
      |                                ^
      |                                 = nullptr

[shakedregev]

Looks good and tests pass. Just add tests for rectangular matrices and let's make sure they still pass.

[shakedregev]

Tests pass and all comments addressed. Approving