Tidy up ID and everseen layers
|Reported by:||magnate||Owned by:||noz|
Everseen status of affixes and themes is set in the _is_known functions, which are checked repeatedly from obj_desc. This isn't right, really. We should store o_ptr->affix_known and o_ptr->theme_known, and use those in obj_desc without calling ID functions. We should then completely tidy up ID, getting rid of all remaining references to o_ptr->ego, and sorting out the impact of rune-based ID on pseudo. (Stuff which pseudos from runes needs to be marked "sensed" at the very least, so the timed sensing doesn't trigger later.)
We can then remove the o_ptr->ego structure element and tidy up savefiles. This should be done at the same time as #1569, as they both mean a new version of rd_item.