Simplify our Assert infrastructure a little.

Simplify our Assert infrastructure a little.

Remove the Trap and TrapMacro macros, which were nearly unused
and confusingly had the opposite condition polarity from the
otherwise-functionally-equivalent Assert macros.

Having done that, it's very hard to justify carrying the errorType
argument of ExceptionalCondition, so drop that too, and just
let it assume everything's an Assert.  This saves about 64K
of code space as of current HEAD.

Discussion: https://postgr.es/m/3928703.1665345117@sss.pgh.pa.us