Add ReSolve CSR Matrix

[alexander-novo]

Description

Adds the ReSolve Csr matrix class to GridKit, with minimal changes:

• Namespaces have been changed to be consistent with GridKit
• Csr class has been changed to CsrMatrix
• ReSolve logging code has been removed, and replaced with std::cerr
• GPU structure has been commented out to be ported later

Tracking issue: #261

Checklist

• All tests pass.
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows GridKit™ 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.
• I have updated CHANGELOG.md to reflect the changes in this PR. If this is a minor PR that is part of a larger fix already included in the file, state so.

Further comments

Follow-up PR will merge Sparse into CsrMatrix.

Something I'd like to fix is the potential to double free if the matrix is copied. This should probably be fixed by removing the ability to copy the matrix.

[pelesh]

Great job! A couple of items to address before this can be merged:

• Remove Sparse base class and include its content in CsrMatrix.
• Remove LinAlgWorkspaceCpu class. It is not needed here.

There are a few other mainly nitpicking issues I suggest we address.

[pelesh]

Follow-up PR will merge Sparse into CsrMatrix.

I suggest you merge Sparse into CsrMatrix in this PR. It is a minor modification.

[pelesh]

Something I'd like to fix is the potential to double free if the matrix is copied. This should probably be fixed by removing the ability to copy the matrix.

Perhaps just implement the assignment operator and make it private method for now? I would leave this for a different PR though.

[alexander-novo]

@pelesh I would prefer deleting any copy operators. Implicitly copying something like a CSR matrix is a fast track to difficult to find performance decreases for no good reason.

[shakedregev]

Documentation needs improvement. Otherwise, just the things we discussed.

[pelesh]

Almost there. The CsrMatrix needs to be implemented as a class template. There are a few other nitpicking issues I suggest we address.

[pelesh]

Looks good. I suggest you fix a few warnings popping up and rebase. We can merge then.

[pelesh]

All review comments addressed.