MNT: Move utils.timer to astroquery #8898

@saimn and @astrofrog has brought up that https://github.com/astropy/astropy/blob/master/astropy/utils/timer.py is only used by astroquery.vo_conesearch (used to be astropy.vo.conesearch) and nothing else in the core, and thus should be moved to astroquery.

1. Do the move and deprecate the one in astropy.
2. Remove it from astropy after a deprecation period.

Is Step 1 a good thing for 4.0?

Progress

• Move code to astroquery -- Move timer functions from astropy astroquery#1508 -- get it merged
• Deprecate the functions here. Remove the user-facing doc. -- MNT: Deprecate utils.timer  #9038
• Open follow-up issue to completely remove the functions after a deprecation period. Also add a note to remove the static PNG from doc. -- MNT: Remove deprecated utils.timer module #9050