Comprehensively exercise each function in the test suite

[manopapad]

Each supported function should be fully exercised in the test suite, e.g.:

• all datatypes supported for the operation
• all supported options
• using a where array, if supported by the operation
• all broadcasting modes
• all cases of implicit up-casting (e.g. adding an integer and a real array) -- we should test at least every combination of an integer, a floating point and a complex array
• other cases of store transformations on inputs (e.g. slice, transpose)
• all array dimensions, up to the max number of dimensions that Legate was compiled for
• passing existing arrays as outputs

To keep things sane, each of the above parameters can be tested in isolation.

To cover an arbitrary amount of dimensions it will be necessary to programmatically generate inputs, e.g. see https://github.com/nv-legate/legate.numpy/blob/896f4fd9b32db445da6cdabf7b78d523fca96936/tests/binary_op_broadcast.py and https://github.com/nv-legate/legate.numpy/blob/067a541905bf3bfc8d3727c6e1fe97a4855729b9/tests/intra_array_copy.py.

The NumPy test suite may be a good starting point, see #22.