LiFuser-BP: merging function issues

[holly avinash]

In version 8.0, When merging two data, it takes a long time to respond after clicking optimize.

[GVI Other Series]

There is no manual alignment, the merging function should do the coarse alignment manually first, so that the SLAM can find the approximate orientation, and then do the automatic alignment. Otherwise, two point clouds with more misalignments can not be automatically merged together. Manually align and wait for RSME to turn green, then click optimize.