Revert "[heap] Refactor methods and nested class of ConcurrentMarkingVisitor"

This reverts commit 6925bc09.

Reason for revert: Speculative revert for roll failures: https://ci.chromium.org/ui/p/chromium/builders/try/linux_optional_gpu_tests_rel/85744/overview

Original change's description:
> [heap] Refactor methods and nested class of ConcurrentMarkingVisitor
>
> This CL moves a few methods and nested class SlotSnapshottingVisitor
> from ConcurrentMarkingVisitor to ConcurrentMarkingVisitorUtility.
>
> Methods in ConcurrentMarkingVisitorUtility are now static and instead have a Visitor parameter.
>
> This is preparatory work for adding a
> YoungGenerationConcurrentMarkingVisitor class, which will be able to
> reuse members of ConcurrentMarkingVisitorUtility.
>
> Bug: v8:13012
> Change-Id: I503c20e655578031018a2e37dd92c1d61bbe1686
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3779677
> Commit-Queue: Leon Bettscheider <bettscheider@google.com>
> Reviewed-by: Omer Katz <omerkatz@chromium.org>
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#81931}

Bug: v8:13012
Change-Id: If2240b2e0769b04d752caefceb95609c6b950bb2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3787373
Owners-Override: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81945}

src/heap/marking-visitor.h

@@ -220,11 +220,6 @@ class MarkingVisitorBase : public HeapVisitor<int, ConcreteVisitor> {
 #endif
   }
 
-  bool is_shared_heap() { return is_shared_heap_; }
-
-  // Marks the object grey and pushes it on the marking work list.
-  V8_INLINE void MarkObject(HeapObject host, HeapObject obj);
-
  protected:
   ConcreteVisitor* concrete_visitor() {
     return static_cast<ConcreteVisitor*>(this);
@@ -264,6 +259,8 @@ class MarkingVisitorBase : public HeapVisitor<int, ConcreteVisitor> {
   // list and visits its header. Returns the size of the descriptor array
   // if it was successully marked as black.
   V8_INLINE int MarkDescriptorArrayBlack(DescriptorArray descriptors);
+  // Marks the object grey and pushes it on the marking work list.
+  V8_INLINE void MarkObject(HeapObject host, HeapObject obj);
 
   V8_INLINE void AddStrongReferenceForReferenceSummarizer(HeapObject host,
                                                           HeapObject obj) {