### What changes were proposed in this pull request?
1, for huber, make it support virtual centering
2, for `LeastSquares`, it was impled in this way: optimize the linear part and then estimate the intercept. So just re-org the its agg and suite to keep in line with other aggs.
### Why are the changes needed?
for better convergence
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
existing and newly added testsuites
Closes#32759 from zhengruifeng/refactor_huber_agg.
Authored-by: Ruifeng Zheng <ruifengz@foxmail.com>
Signed-off-by: Ruifeng Zheng <ruifengz@foxmail.com>
ffc61c6af0