Fix assorted bugs by changing TS_execute's callback API to ternary logic.

 Fix assorted bugs by changing TS_execute's callback API to ternary logic.
 
 Text search sometimes failed to find valid matches, for instance
 '!crew:A'::tsquery might fail to locate 'crew:1B'::tsvector during
 an index search.  The root of the issue is that TS_execute's callback
 functions were not changed to use ternary (yes/no/maybe) reporting
 when we made the search logic itself do so.  It's somewhat annoying
 to break that API, but on the other hand we now see that any code
 using plain boolean logic is almost certainly broken since the
 addition of phrase search.  There seem to be very few outside callers
 of this code anyway, so we'll just break them intentionally to get
 them to adapt.
 
 This allows removal of tsginidx.c's private re-implementation of
 TS_execute, since that's now entirely duplicative.  It's also no
 longer necessary to avoid use of CALC_NOT in tsgistidx.c, since
 the underlying callbacks can now do something reasonable.
 
 Back-patch into v13.  We can't change this in stable branches,
 but it seems not quite too late to fix it in v13.
 
 Tom Lane and Pavel Borisov
 
 Discussion: https://postgr.es/m/CALT9ZEE-aLotzBg-pOp2GFTesGWVYzXA3=mZKzRDa_OKnLF7Mg@mail.gmail.com