Sparse CSR: Add tensor.resize_ and tensor.copy_ (#63510)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63510
Sparse CSR matrix resizing behavior:
If we _increase the number of rows_ the number of specified elements in the matrix remains the same -> the size of col_indices, values doesn't change, the size of crow_indices becomes `rows+1`.
If we _decrease the number of rows_ the number of specified elements will be `min(nnz, rows*cols)` -> need to resize `crow_indices` to `rows+1` and set the last element to `min(nnz, rows*cols)`; decrease the size of col_indices and values to `min(nnz, rows*cols)`.
If we _increase the number of columns_ the number of specified elements in the matrix remains the same, the number of rows remains the same -> no need to resize anything, just set new sizes.
We _cannot decrease the number of columns_ because it would require recomputing `crow_indices`.
cc nikitaved pearu cpuhrsch IvanYashchuk
Test Plan: Imported from OSS
Reviewed By: anjali411
Differential Revision: D31796680
Pulled By: cpuhrsch
fbshipit-source-id: 7d8a9701ce06d30a1841f94bba0a057cacea9401
