Fast-matrix-market

* Close files more quickly

Reduce memory usage on parallel reads
Reduce compilation time and library size by coalescing some code paths
Fix CSC write insufficient parallelism issue
Add write_matrix_market_csc
Flush streams at the end of write (fixes some PyPy issues)
Compile on 32-bit systems
Permit fully indented .mtx files
Improved multiline comments
Add compile-time option to exclude vector support
Add option to always include comment line, even if empty (match SciPy behavior)
Python: open files in binary mode which fixes some compatibility issues on Windows
Python: Fix seek on sync crash with StringIO, manifested in mminfo of StringIO objects
Python: find symmetry on small matrices by default

Change thread pool to task-thread-pool

* Be permissive about leading whitespace in banner
* Ensure skew-symmetric matrices are not loaded into an unsigned type
* Adding GraphBLAS to Ubuntu CI Runs

* Armadillo bindings
* Small SciPy compatibility improvements (no closing StringIO stream, match out-of-range value handling, complete pass of SciPy's mmio test suite)
* Allow empty lines anywhere in MatrixMarket file
* Upgrade to fast_float 4.0.0

Add GraphBLAS bindings