ARC: cycle detector (#12823)

* first implementation of the =trace and =dispose hooks for the cycle collector
* a cycle collector for ARC: progress
* manual: the .acyclic pragma is a thing once again
* gcbench: adaptations for --gc:arc
* enable valgrind tests for the strutils tests
* testament: better valgrind support
* ARC refactoring: growable jumpstacks
* ARC cycle detector: non-recursive algorithm
* moved and renamed core/ files back to system/
* refactoring: --gc:arc vs --gc:orc since 'orc' is even more experimental and we want to ship --gc:arc soonish

compiler/ast.nim

@@ -478,7 +478,7 @@ type
     nfExecuteOnReload  # A top-level statement that will be executed during reloads
 
   TNodeFlags* = set[TNodeFlag]
-  TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: ~38)
+  TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: ~39)
     tfVarargs,        # procedure has C styled varargs
                       # tyArray type represeting a varargs list
     tfNoSideEffect,   # procedure type does not allow side effects
@@ -537,6 +537,7 @@ type
     tfContravariant   # contravariant generic param
     tfCheckedForDestructor # type was checked for having a destructor.
                            # If it has one, t.destructor is not nil.
+    tfAcyclic # object type was annotated as .acyclic
 
   TTypeFlags* = set[TTypeFlag]
 
@@ -635,7 +636,7 @@ type
     mSwap, mIsNil, mArrToSeq, mCopyStr, mCopyStrLast,
     mNewString, mNewStringOfCap, mParseBiggestFloat,
     mMove, mWasMoved, mDestroy,
-    mDefault, mUnown, mAccessEnv, mReset,
+    mDefault, mUnown, mAccessEnv, mAccessTypeInfo, mReset,
     mArray, mOpenArray, mRange, mSet, mSeq, mOpt, mVarargs,
     mRef, mPtr, mVar, mDistinct, mVoid, mTuple,
     mOrdinal,
@@ -870,6 +871,8 @@ type
     attachedDestructor,
     attachedAsgn,
     attachedSink,
+    attachedTrace,
+    attachedDispose,
     attachedDeepCopy
 
   TType* {.acyclic.} = object of TIdObj # \
@@ -1298,7 +1301,8 @@ const
   UnspecifiedLockLevel* = TLockLevel(-1'i16)
   MaxLockLevel* = 1000'i16
   UnknownLockLevel* = TLockLevel(1001'i16)
-  AttachedOpToStr*: array[TTypeAttachedOp, string] = ["=destroy", "=", "=sink", "=deepcopy"]
+  AttachedOpToStr*: array[TTypeAttachedOp, string] = [
+    "=destroy", "=", "=sink", "=trace", "=dispose", "=deepcopy"]
 
 proc `$`*(x: TLockLevel): string =
   if x.ord == UnspecifiedLockLevel.ord: result = "<unspecified>"