BitMap is an abstract class. All subclasses provide their own allocators. It is the allocator brings the capability to 'resize' the container. I would like to add a new 'GrowableBitmap' and make it the common base class.

A new interface 'grow(idx_t bit)' will be added to the class.

To substitute 'VectorSet', we also need to merge ResourceBitMap and ArenaBitMap because VectorSet supports Resource and Arena storage at the same time.