[C++][Python] Helper to generate boolean masks

[amol-]

Describe the enhancement requested

In various conditions it would be helpful to be able to generate boolean masks that point to specific indices of an array.

For example it can be combined with if_else compute functions to merge two arrays by picking exactly which rows should come from each of one the arrays. Or combined with replace_with_mask to set rows in an array.

At the moment there is no easy way to create such a mask

Component(s)

C++, Python