rework SymbolFactory

- rename & move to Pilz.UI..Telerik.Symbols.RadSymbolFactory
- make default implementaiton available at Pilz.UI.Symbols.SymbolFactory
- add interfaces

Pilz.UI/Symbols/ISymbolFactory.cs

@@ -0,0 +1,12 @@
+using System.Reflection;
+
+namespace Pilz.UI.Symbols;
+
+public interface ISymbolFactory<TSymbols>
+{
+    Image? GetImage(TSymbols svgImage, Size size);
+    Image? GetImage(TSymbols svgImage, SymbolSize size);
+    Assembly GetImageResourceAssembly();
+    string GetImageRessourcePath(TSymbols svgImage);
+    Stream? GetImageRessourceStream(TSymbols svgImage);
+}