Deprecate QgsDataItem API for setting item CRS

This is no longer used by QGIS (it was only ever used by the standalone
browser)

(cherry picked from commit d61694c)

Author: nyalldawson

python/core/auto_generated/qgsdataitem.sip.in

@@ -205,10 +205,12 @@ Items that return valid URI will be returned in mime data when dragging a select
     typedef QFlags<QgsDataItem::Capability> Capabilities;
 
 
-    virtual bool setCrs( const QgsCoordinateReferenceSystem &crs );
+ virtual bool setCrs( const QgsCoordinateReferenceSystem &crs ) /Deprecated/;
 %Docstring
 Writes the selected crs into data source. The original data source will be modified when calling this
 method.
+
+.. deprecated:: since QGIS 3.6. This method is no longer used by QGIS and will be removed in QGIS 4.0.
 %End
 
     virtual bool rename( const QString &name );

src/core/qgsdataitem.h

@@ -207,7 +207,7 @@ class CORE_EXPORT QgsDataItem : public QObject
     enum Capability
     {
       NoCapabilities    = 0,
-      SetCrs            = 1 << 0, //!< Can set CRS on layer or group of layers
+      SetCrs            = 1 << 0, //!< Can set CRS on layer or group of layers. \deprecated in QGIS 3.6 -- no longer used by QGIS and will be removed in QGIS 4.0
       Fertile           = 1 << 1, //!< Can create children. Even items without this capability may have children, but cannot create them, it means that children are created by item ancestors.
       Fast              = 1 << 2, //!< CreateChildren() is fast enough to be run in main thread when refreshing items, most root items (wms,wfs,wcs,postgres...) are considered fast because they are reading data only from QgsSettings
       Collapse          = 1 << 3,  //!< The collapse/expand status for this items children should be ignored in order to avoid undesired network connections (wms etc.)
@@ -218,8 +218,14 @@ class CORE_EXPORT QgsDataItem : public QObject
     /**
      * Writes the selected crs into data source. The original data source will be modified when calling this
      * method.
+     *
+     * \deprecated since QGIS 3.6. This method is no longer used by QGIS and will be removed in QGIS 4.0.
      */
-    virtual bool setCrs( const QgsCoordinateReferenceSystem &crs ) { Q_UNUSED( crs ); return false; }
+    Q_DECL_DEPRECATED virtual bool setCrs( const QgsCoordinateReferenceSystem &crs ) SIP_DEPRECATED
+    {
+      Q_UNUSED( crs );
+      return false;
+    }
 
     /**
      * Sets a new \a name for the item, and returns true if the item was successfully renamed.