Bug 1765018 - part 7: Make some methods which return an instance (not reference) of EditorDOMPointBase be template methods r=m_kato

For avoiding to use `To<EditorDOMPoint>()` etc from temporary object, such
methods should be templated.

Differential Revision: https://phabricator.services.mozilla.com/D143884

editor/libeditor/HTMLEditorDataTransfer.cpp

@@ -463,7 +463,8 @@ HTMLEditor::HTMLWithContextInserter::GetNewCaretPointAfterInsertingHTML(
         wsRunScannerAtStartReason.ScanPreviousVisibleNodeOrBlockBoundaryFrom(
             pointToPutCaret);
     if (backwardScanFromPointToCaretResult.InVisibleOrCollapsibleCharacters()) {
-      pointToPutCaret = backwardScanFromPointToCaretResult.Point();
+      pointToPutCaret =
+          backwardScanFromPointToCaretResult.Point<EditorDOMPoint>();
     } else if (backwardScanFromPointToCaretResult.ReachedSpecialContent()) {
       // XXX In my understanding, this is odd.  The end reason may not be
       //     same as the reached special content because the equality is