add default field support for object in ARC/ORC (#20480)

* fresh start

* add cpp target

* add result support

* add nimPreviewRangeDefault

* reduce

* use orc

* refactor common parts

* add tuple support

* add testcase for tuple

* cleanup; fixes nimsuggest tests

* there is something wrong with cpp

* remove

* add support for seqs

* fixes style

* addd initial distinct support

* remove links

* typo

* fixes tuple defaults

* add rangedefault

* add cpp support

* fixes one more bugs

* add more hasDefaults

* fixes ordinal types

* add testcase for #16744

* add testcase for #3608

* fixes docgen

* small fix

* recursive

* fixes

* cleanup and remove tuple support

* fixes nimsuggest

* fixes generics procs

* refactor

* increases timeout

* refactor hasDefault

* zero default; disable i386

* add tuples back

* fixes bugs

* fixes tuple

* add more tests

* fix one more bug regarding tuples

* more tests and cleanup

* remove messy distinct types which must be initialized by original types

* add tests

* fixes zero default

* fixes grammar

* fixes tests

* fixes tests

* fixes tests

* fixes comments

* fixes and add testcase

* undo default values for results

Co-authored-by: flywind <43030857+xflywind@users.noreply.github.com>

lib/system/seqs_v2.nim

@@ -125,6 +125,8 @@ proc setLen[T](s: var seq[T], newlen: Natural) =
       if xu.p == nil or xu.p.cap < newlen:
         xu.p = cast[typeof(xu.p)](prepareSeqAdd(oldLen, xu.p, newlen - oldLen, sizeof(T), alignof(T)))
       xu.len = newlen
+      for i in oldLen..<newlen:
+        xu.p.data[i] = default(T)
 
 proc newSeq[T](s: var seq[T], len: Natural) =
   shrink(s, 0)