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.

tests/stdlib/tstdlib_issues.nim

@@ -43,7 +43,7 @@ block tcount:
 
   # bubble sort
   for i in low(arr)..high(arr):
-    for j in i+1..high(arr): # Error: unhandled exception: value out of range: 5 [RangeError]
+    for j in i+1..high(arr): # Error: unhandled exception: value out of range: 5 [RangeDefect]
       if arr[i] > arr[j]:
         let tmp = arr[i]
         arr[i] = arr[j]