Error -> Defect for defects (#13908)

* Error -> Defect for defects

The distinction between Error and Defect is subjective,
context-dependent and somewhat arbitrary, so when looking at an
exception, it's hard to guess what it is - this happens often when
looking at a `raises` list _without_ opening the corresponding
definition and digging through layers of inheritance.

With the help of a little consistency in naming, it's at least possible
to start disentangling the two error types and the standard lib can set
a good example here.

compiler/sempass2.nim

@@ -752,7 +752,7 @@ proc track(tracked: PEffects, n: PNode) =
       createTypeBoundOps(tracked, n[0].typ, n.info)
     else:
       # A `raise` with no arguments means we're going to re-raise the exception
-      # being handled or, if outside of an `except` block, a `ReraiseError`.
+      # being handled or, if outside of an `except` block, a `ReraiseDefect`.
       # Here we add a `Exception` tag in order to cover both the cases.
       addEffect(tracked, createRaise(tracked.graph, n), nil)
   of nkCallKinds: