Convert unnest(bitmap_to_array(xxx)) to unnest_bitmap

[trueeyu]

Enhancement

Current users allways use unnest(bitmap_to_array(xxx)) to unnest bitmap.

There are two problems with this usage.

1. Poor performance and high memory usage.
2. It will be limited by the length of array.

Current unnest_bitmap(xxx) was supported, and it is best to be able to automatically convert.