Use validation tolerance in Core::tolerance

It is important that the same value is used everywhere. Otherwise,
validation could miss problems that then end up in an exported file,
for example.

crates/fj-core/src/core.rs

@@ -41,7 +41,7 @@ impl Core {
 
     /// Access the tolerance value used for intermediate geometry representation
     pub fn tolerance(&self) -> Tolerance {
-        self.default_tolerance
+        self.layers.validation.config.tolerance
     }
 }