[C++] Add BinaryDataBuilder class

### Describe the enhancement requested

As mentioned [here](https://github.com/apache/arrow/issues/50249#issuecomment-4845252004), it would be beneficial to have a class that knows the validity bitmap bits in advance and can directly build binary types from data buffers.

### Component(s)

C++

Start by reading the discussion linked from issue 50249 to understand the motivation and expected behavior for BinaryDataBuilder. Then inspect the relevant C++ binary-type construction APIs; done means a class can use validity bitmap bits known in advance to build binary types directly from data buffers.

Written by the indexing model from the issue text.