feat: flexibiilty in brute-force computation

[yucongalicechen]

We want to allow users to modify the global parameters N_POINTS_ON_DIAMETER (the number of points on each diameter to sample the circle) and TTH_GRID (the range of angles) when using the brute-force method.
Have compute_cve(input_pattern, mud, method="polynomial_interpolation", xtype="tth", n_points_on_diameter=None, tth_grid=None) so that people can pass in different n_points_on_diameter and tth_grid as they wish.
Refer to #163 for more details.