[WIP] Fix slow rebuild after data source assignment

[Copilot]

Analyzing slow rebuild performance issue when using SetData

• Explored repository structure and identified key files
• Identified the performance issue: Rebuild() unnecessarily calls RunGetData() even when data is already cached via SetData()
• Implement elegant solution: Add a method to skip RunGetData() when data is already set
• Test the changes
• Run security checks

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Solved inelegantly] Rebuild very slow after a datable is assigned to a dataset in the rdl</issue_title>
<issue_description>I wrote this method in a my class;
public void SetDataSource(DataTable TableSource, int DataSetPosition) {
int Counter = 0;

  	foreach(fyiReporting.RDL.DataSet D in  Viewer.Report.DataSets) {
  		if(Counter == DataSetPosition) {
  			D.SetData(TableSource);
  			break;
  		}
  		Counter++;
  	}
  	//Very Slow
  	Viewer.Rebuild();
  }

but even if in the table there are few records the rebuild is very slow.
</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #183

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