TextEditor: Remove one stack of EditorWidget constructors

There are conceptually only two: one that operates a new document,
and one that shares one. Being explicit makes moving data over to
the Editor hierarchy easier. Convenience can be re-added there,
later.

Change-Id: I9b34ff26628c99ffff01201dcf99332d5e7253e9
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/cpptools/cpppointerdeclarationformatter_test.cpp

@@ -104,7 +104,7 @@ public:
         // Open file
         auto textDocument = new TextEditor::BaseTextDocument;
         textDocument->setId(Core::Constants::K_DEFAULT_TEXT_EDITOR_ID);
-        TextEditor::BaseTextEditorWidget editorWidget(textDocument);
+        TextEditor::BaseTextEditorWidget editorWidget(textDocument, 0);
         editorWidget.setupAsPlainEditor();
         QString error;
         editorWidget.open(&error, document->fileName(), document->fileName());