Added methods to diagonally scale csr matrices on the left and right.

[shakedregev]

Description

This is necessary to solve the issue of L and U being in the right format. See details here. Additionally, diagonal scaling is needed for SUNDIALS and HyKKT integration.

1 of the 2 steps necessary to close issue 251

Mentions @(user)

Proposed changes

I added methods to diagonally scale CSR matrices on the left and right. This will allow the use of external codes and moving the unit diagonal when we transpose and switch L and U by interpreting their CSC representation as CSR. New unit tests pass.

Checklist

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• All tests pass. Code tested on
  • CPU backend
  • CUDA backend
  • HIP backend
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
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• 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

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[shakedregev]

A clarification: The different order of arguments for leftDiagonalScale(vector_type diag, matrix::Csr A) and rightDiagonalScale(matrix::Csr A, vector_type diag) is intentional to reflect the mathematics. There is no danger of the code compiling if the order of the arguments is switched. The functions have a different stamp so that the user is intentional about which one to call.

[shakedregev]

Closing this as it is broken. Replaced by #283.