Is your feature request related to a problem or challenge? Please describe what you are trying to do.

To replace NullBufferBuilder with BooleanBufferBuilder for optimization in DataFusion , some public methods are needed to be implemented in NullBufferBuilder with BooleanBufferBuilder to access inner builder.

Describe the solution you'd like

I would like to add methods like BooleanBufferBuilder :

• get_bit()
• capacity
• truncate()

Describe alternatives you've considered

Other strategies below also may access the inner builder:

• make the inner builder public
• add a method that can return the reference of the inner builder

Additional context

Related issue

Use NullBufferBuilder instead of BooleanBufferBuilder for creating Null masks #14115