defaults to ORC (#19972)

* defaults to Orc

* bootstrap using refc

* use gc

* init orc defines

* unregister orc

* fix gc

* fix commands

* add prepareMutation for orc

* enable deepcopy for orc

* prepareMutation

* more fixes

* some cases

* bug #20081

* partial fixes

* partial fixes

* fixes command line

* more fixes

* build Nim with refc

* use gc

* more fixes

* rstore

* orc doesn't support threadpool

* more shallowCopy

* more fixes

* fixes unsafeNew

* workarounds

* small

* more fixes

* fixes some megatest

* tcodegenbugs1 refc

* fxies megatest

* build nimble with refc

* workaround tensordsl tests

* replace shallowCopy with move

* fixes action

* workaround

* add todo

* fixes important packages

* unpublic unregisterArcOrc

* fixes cpp

* enable windows

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

tests/objects/t4318.nim

@@ -1,3 +1,8 @@
+discard """
+  matrix: "--mm:refc"
+"""
+
+
 type
   A = object of RootObj
   B = object of A

tests/objects/tobj_asgn_dont_slice.nim

@@ -1,4 +1,5 @@
 discard """
+  matrix: "--mm:refc"
   outputsub: '''ObjectAssignmentDefect'''
   exitcode: "1"
 """

tests/objects/tobjconstr.nim

@@ -50,27 +50,30 @@ type
   BS = object of B
   C = object of BS
     z*: int
-# inherited fields are ignored, so no fields are set
-when true:
-  var
-    o: B
-  o = B(x: 123)
-  echo o
-  o = B(y: 678, x: 123)
-  echo o
 
-# inherited fields are ignored
-echo C(x: 128, z: 89)          # (y: 0, x: 0)
-echo B(y: 678, x: 123)  # (y: 678, x: 0)
-echo B(x: 123, y: 678)  # (y: 678, x: 0)
+proc main2 =
+  # inherited fields are ignored, so no fields are set
+  when true:
+    var
+      o: B
+    o = B(x: 123)
+    echo o
+    o = B(y: 678, x: 123)
+    echo o
 
-when true:
-  # correct, both with `var` and `let`;
-  var b=B(x: 123)
-  echo b                  # (y: 0, x: 123)
-  b=B(y: 678, x: 123)
-  echo b                  # (y: 678, x: 123)
-  b=B(y: b.x, x: b.y)
-  echo b                  # (y: 123, x: 678)
+  # inherited fields are ignored
+  echo C(x: 128, z: 89)          # (y: 0, x: 0)
+  echo B(y: 678, x: 123)  # (y: 678, x: 0)
+  echo B(x: 123, y: 678)  # (y: 678, x: 0)
 
+  when true:
+    # correct, both with `var` and `let`;
+    var b=B(x: 123)
+    echo b                  # (y: 0, x: 123)
+    b=B(y: 678, x: 123)
+    echo b                  # (y: 678, x: 123)
+    b=B(y: b.x, x: b.y)
+    echo b                  # (y: 123, x: 678)
+
+main2()
 GC_fullCollect()