[Refactoring] Moving between TreeScopes should be done by its own class.

      https://bugs.webkit.org/show_bug.cgi?id=75290

Reviewed by Ryosuke Niwa.

This change extracted Node::setTreeScopeRecursively(),
setDocumentRecursively() and a part of setDocument() into a new
class called TreeScopeAdopter. By doing this, the idea of
moving a node from scope to scope, that was originally hidden
behind the forest of Node APIs, has become clearer.

Note that this change is a preparation for Bug 59816.

No new tests. No behavioral change.

* CMakeLists.txt:
* GNUmakefile.list.am:
* Target.pri:
* WebCore.gypi:
* WebCore.vcproj/WebCore.vcproj:
* WebCore.xcodeproj/project.pbxproj:
* dom/ContainerNode.cpp: Followed the renaming.
(WebCore::ContainerNode::takeAllChildrenFrom):
(WebCore::ContainerNode::insertBefore):
(WebCore::ContainerNode::replaceChild):
(WebCore::ContainerNode::removeBetween):
(WebCore::ContainerNode::removeChildren):
(WebCore::ContainerNode::appendChild):
(WebCore::ContainerNode::parserAddChild):
* dom/DOMAllInOne.cpp:
* dom/Document.cpp: Followed te renaming.
(WebCore::Document::setDocType):
(WebCore::Document::adoptNode):
* dom/Element.cpp: Followed te renaming.
(WebCore::Element::removeShadowRoot):
* dom/Node.cpp:
(WebCore::Node::setDocument):
(WebCore::Node::setTreeScope):
(WebCore::Node::didMoveToNewDocument):
* dom/Node.h:
* dom/TreeScope.h:
* dom/TreeScope.cpp:
(WebCore::TreeScope::adoptIfNeeded): moved from setTreeScopeRecursively()
* dom/TreeScopeAdopter.cpp: Added.
(WebCore::TreeScopeAdopter::TreeScopeAdopter):
(WebCore::TreeScopeAdopter::moveTreeToNewScope):
(WebCore::TreeScopeAdopter::moveTreeToNewDocument):
(WebCore::TreeScopeAdopter::ensureDidMoveToNewDocumentWasCalled):
(WebCore::TreeScopeAdopter::moveNodeToNewDocument):
* dom/TreeScopeAdopter.h: Added.
(WebCore::TreeScopeAdopter::ensureDidMoveToNewDocumentWasCalled):
(WebCore::TreeScopeAdopter::execute):
(WebCore::TreeScopeAdopter::needsScopeChange()):
(WebCore::TreeScopeAdopter::shadowRootFor):

git-s