[gdal] Implement the data provider reloadData() function (fixes #20536)

Author: nirvn

src/providers/gdal/qgsgdalprovider.cpp

@@ -526,6 +526,15 @@ void QgsGdalProvider::closeDataset()
   closeCachedGdalHandlesFor( this );
 }
 
+void QgsGdalProvider::reloadData()
+{
+  QMutexLocker locker( mpMutex );
+  closeDataset();
+
+  mHasInit = false;
+  ( void )initIfNeeded();
+}
+
 QString QgsGdalProvider::htmlMetadata()
 {
   QMutexLocker locker( mpMutex );

src/providers/gdal/qgsgdalprovider.h

@@ -171,6 +171,8 @@ class QgsGdalProvider : public QgsRasterDataProvider, QgsGdalProviderBase
     bool setNoDataValue( int bandNo, double noDataValue ) override;
     bool remove() override;
 
+    void reloadData() override;
+
     QString validateCreationOptions( const QStringList &createOptions, const QString &format ) override;
     QString validatePyramidsConfigOptions( QgsRaster::RasterPyramidsFormat pyramidsFormat,
                                            const QStringList &configOptions, const QString &fileFormat ) override;