[C++] Add `OptionalBitmapAnd` utility

[pitrou]

Describe the enhancement requested

We currently have BitmapAnd utility functions that return the conjunction of two bitmaps.
However, null bitmaps are optional which complicates things when conjoining two null bitmaps. It would be good to centralize that functionality in a dedicated utility function, for example:

ARROW_EXPORT
Result<std::shared_ptr<Buffer>> OptionalBitmapAnd(
    MemoryPool* pool,
    const std::shared_ptr<Buffer>& left, int64_t left_offset,
    const std::shared_ptr<Buffer>& right, int64_t right_offset,
    int64_t length, int64_t out_offset);

Component(s)

C++

[pitrou]

cc @raulcd

[Shockp]

Hi @raulcd and @pitrou! I recently got my first C++ PR merged and am looking for a good second issue. I see this is assigned to Raul, are you actively working on this, or is it open for a community contribution?

[raulcd]

I pretty much have this abandoned so feel free to give it a go! I'll assign you the issue.

[Shockp]

I will get started on the OptionalBitmapAnd implementation right away. Also, I noticed you are spanish as well :).

[Shockp]

@raulcd @pitrou, I have an initial implementation ready for testing. Should I add these tests to bitmap_test.cc? I noticed there isn't a bitmap_ops_test.cc; given that bitmap_test.cc is already over 1,500 lines, it might be a good time to create bitmap_ops_test.cc and refactor the relevant operation tests there to keep the codebase maintainable.