rewrite editor info bar handling

the info about the bars is now stored in the IFile, not in the
EditorView. this is somewhat more expensive for the bars which
identically apply to all editors of one type, but fixes consistency
issues between views.

additionally, it is now possible to set several simultaneous
info bars per file, which ensures that no information is lost.

Co-authored-by: mae

src/plugins/texteditor/basetexteditor.h

@@ -323,6 +323,7 @@ protected:
 
 private:
     void maybeSelectLine();
+    void updateCannotDecodeInfo();
 
 public:
     void duplicateFrom(BaseTextEditorWidget *editor);
@@ -343,7 +344,6 @@ private slots:
     void setFindScope(const QTextCursor &start, const QTextCursor &end, int, int);
     bool inFindScope(const QTextCursor &cursor);
     bool inFindScope(int selectionStart, int selectionEnd);
-    void currentEditorChanged(Core::IEditor *editor);
     void inSnippetMode(bool *active);
 
 private: