BUG: sparse: `setdiag` broken when not entire diagonal belongs to sparsity pattern

[sdrave]

Describe your issue.

setdiag yields incorrect results when it is called on a CSR matrix that has a few diagonal entries missing in its sparsity pattern.

Reproducing Code Example

import numpy as np
import scipy.sparse as sps

A = sps.eye(1002, format='csr')
A[1,1] = 0
A.eliminate_zeros()

A.setdiag(np.zeros(A.shape[0]))
assert A[-1,-1] == 0

Error message

The assertion fails.

SciPy/NumPy/Python version and system information

1.15.0.dev0+git20241031.846d79e 1.26.4 sys.version_info(major=3, minor=12, micro=2, releaselevel='final', serial=0)
Build Dependencies:
  blas:
    detection method: pkgconfig
    found: true
    include directory: /usr/include/x86_64-linux-gnu/openblas-pthread/
    lib directory: /usr/lib/x86_64-linux-gnu/openblas-pthread/
    name: openblas
    openblas configuration: USE_64BITINT= DYNAMIC_ARCH=1 DYNAMIC_OLDER=1 NO_CBLAS=
      NO_LAPACK= NO_LAPACKE=1 NO_AFFINITY=1 USE_OPENMP=0 generic MAX_THREADS=64
    pc file directory: /usr/lib/x86_64-linux-gnu/pkgconfig
    version: 0.3.21
  lapack:
    detection method: pkgconfig
    found: true
    include directory: /usr/include/x86_64-linux-gnu/openblas-pthread/
    lib directory: /usr/lib/x86_64-linux-gnu/openblas-pthread/
    name: openblas
    openblas configuration: USE_64BITINT= DYNAMIC_ARCH=1 DYNAMIC_OLDER=1 NO_CBLAS=
      NO_LAPACK= NO_LAPACKE=1 NO_AFFINITY=1 USE_OPENMP=0 generic MAX_THREADS=64
    pc file directory: /usr/lib/x86_64-linux-gnu/pkgconfig
    version: 0.3.21
  pybind11:
    detection method: config-tool
    include directory: unknown
    name: pybind11
    version: 2.13.6
Compilers:
  c:
    commands: cc
    linker: ld.bfd
    name: gcc
    version: 12.2.0
  c++:
    commands: c++
    linker: ld.bfd
    name: gcc
    version: 12.2.0
  cython:
    commands: cython
    linker: cython
    name: cython
    version: 3.0.11
  fortran:
    commands: gfortran
    linker: ld.bfd
    name: gcc
    version: 12.2.0
  pythran:
    include directory: ../../../../../tmp/pip-build-env-4s1lehpp/overlay/lib/python3.12/site-packages/pythran
    version: 0.17.0
Machine Information:
  build:
    cpu: x86_64
    endian: little
    family: x86_64
    system: linux
  cross-compiled: false
  host:
    cpu: x86_64
    endian: little
    family: x86_64
    system: linux
Python Information:
  path: [...]/bin/python
  version: '3.12'