Redis adds native compressed bitmaps with Roaring encoding

Redis introduced a new OBJ_BITMAP object type with Roaring encoding backed by the CRoaring library. The compression sharply cuts memory use for large and sparse bitmaps while keeping command semantics and RDB persistence compatible.

• New OBJ_BITMAP type with OBJ_ENCODING_BITMAP_ROARING encoding
• bitmap-default-roaring option auto-creates compressed bitmaps on writes
• SETBIT, GETBIT and bitwise ops work with both formats
• New RDB type stores Roaring bitmaps via compact CRoaring serialization