Update auras when clouds change (#9259)

The following sequence of actions, as a follower of TSO or Dithmenos,
would leave parts of LOS unaffected by halo or umbra:

 1. Read a scroll of Fog: LOS changes but agrid does not, so there
    are out-of-LOS cells that are still affected by the aura.
 2. Take a step: this updates agrid, taking into account the fog,
    so now the cells you can't see are no longer aura-ed.
 3. Single-wait for the fog to expire.  This leaves the agrid unchanged
    again, so the unaura-ed cells from step 2 remain unaura-ed despite
    now being visible

    (Note that waiting too long in step 3 (e.g. with 5-wait) could cause
     auras to be updated for other reasons, hiding the problem).

Use los_terrain_changed instead of invalidate_los_around: the former
calls the latter, but also calls invalidate_agrid, so steps 1 and 3
keep auras in sync with LOS.