The sequence "hl" is easy to type but recalling its function after not
using  it a  while  takes  effort.  Seeing  "Hl-Line  mode enabled  in
current buffer" also takes effort to read.

In the spirit of "display-line-numbers-mode" can "highlight-line-mode"
be the full expansion for feedback and the expansion to "hl"?

Steps to reproduce
  . start "emacs -Q"
  . type three lines of "q"
  . on the middle line type "M-x hl" and TAB to use the completion

An improvement from my point of view
  . on the middle line type "hl" and TAB to use the completion
  . the completion expands what was "hl-line-mode" to "highlight-line-mode"