better nativestacktrace support; refs #15284; backport [1.2] (#15384)

* nimStackTraceOverride: enable stack traces in exceptions

This is a two-step stack trace collection scheme, because re-raised
exceptions will collect multiple stack traces but use them rarely, when
printing info about an uncaught exception, so it makes sense to only do
the cheap stack unwinding all the time and the relatively expensive
debugging information collection on-demand.

`asyncfutures` implements its own `$` proc for printing
`seq[StackTraceEntry]`, so we have to add the debugging info there, just
like we do for the private `$` proc in `system/excpt`.

* cleaned up PR #15284

Co-authored-by: Ștefan Talpalaru <stefantalpalaru@yahoo.com>

lib/pure/asyncfutures.nim

@@ -9,6 +9,8 @@
 
 import os, tables, strutils, times, heapqueue, options, deques, cstrutils
 
+import "system/stacktraces"
+
 # TODO: This shouldn't need to be included, but should ideally be exported.
 type
   CallbackFunc = proc () {.closure, gcsafe.}
@@ -293,7 +295,12 @@ proc getHint(entry: StackTraceEntry): string =
     if cmpIgnoreStyle(entry.filename, "asyncmacro.nim") == 0:
       return "Resumes an async procedure"
 
-proc `$`*(entries: seq[StackTraceEntry]): string =
+proc `$`*(stackTraceEntries: seq[StackTraceEntry]): string =
+  when defined(nimStackTraceOverride):
+    let entries = addDebuggingInfo(stackTraceEntries)
+  else:
+    let entries = stackTraceEntries
+
   result = ""
   # Find longest filename & line number combo for alignment purposes.
   var longestLeft = 0
@@ -308,10 +315,10 @@ proc `$`*(entries: seq[StackTraceEntry]): string =
   # Format the entries.
   for entry in entries:
     if entry.procname.isNil:
-      if entry.line == -10:
+      if entry.line == reraisedFromBegin:
         result.add(spaces(indent) & "#[\n")
         indent.inc(2)
-      else:
+      elif entry.line == reraisedFromEnd:
         indent.dec(2)
         result.add(spaces(indent) & "]#\n")
       continue