[C++] Provide bulk method on TypedBufferBuilder<bool> for appending a bitmap

[asfimport]

We have TypedBufferBuilder<bool>::UnsafeAppend for an array of bytes (where non-zero becomes 1), but it would be useful to have also UnsafeAppendBits so that bitmaps coming from arrow::Array can also be appended

Reporter: Wes McKinney / @wesm

Related issues:

• [C++] Implement Bitmap class to modularize handling of bitmaps (relates to)
• [C++] Provide method on AdaptiveIntBuilder for appending integer Array types (is related to)

_{Note: This issue was originally created as ARROW-5983. Please see the migration documentation for further details.}