Changes to the StackMapTable will result in _frame_count not necessarily being equal to the number of frames reported by a classfile. Additionally, the StackMapTable uses redundant information that can be derived from the StackMapReader which itself has a design that does not align with other readers in the code base.

Caching frequently used data like the previous and current frame in the StackMapReader will help to simplify the constructor for StackMapTable as well as StackMapReader::next().