Related to #35578
Previously int16/int8 bitmap index may read int32 array as int16, which
may cause build index with half of the data(if array is full) and half
zeros. This causes BITMAP index lost information.
This PR matches int8_t & int16_t while `get_data` when building index.
Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>