Update `semlbci` to find the robust LBCI if requested

[sfcheung]

DONE. Test passed. (4d891be886c431c847f87b3f677deb2fb82dba2f, 691e45518f5fbcf060cb44469226bee458530010, e81ef0189f13806cc71d55732bc6b3b6609922bc, 2ba0c6f91db82be4ff06dc78efa8df9015a101e8)

Status:

• Updated check_sem_out. Test passed.
• Added an argument for this option (robust LBCI).
• Add a check for the SEM fit object (sem_out) to see whether robust LBCI is appropriate.
• Revised to pass the argument to ci_i, which will compute the scaling factor for a parameter and pass it to ci_bound_wn_i.
• Store the scaling_factor results from ci_i.

Notes:

• Can do robust LBCI if:

  any(names(sem_out@test) %in% 
  c("satorra.bentler", 
    "yuan.bentler", 
    "yuan.bentler.mplus",
    "mean.var.adjusted",
    "scaled.shifted"))

• Will only use satorra.2000 in the LR test.