[LL API] Fix on-air analysis for scripts (KTIJ-21108)

The implementation is rather limited. Advanced cases, such as
replacing a script with another one with different import directives,
won't work because of non-trivial relationship between 'FirFile' and
'FirScript'.

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/BuilderConfigurator.kt

@@ -357,6 +357,10 @@ object BuilderConfigurator : AbstractBuilderConfigurator<FirTreeBuilder>(FirTree
             fields from resolvedQualifier
         }
 
+        builder(script) {
+            withCopy()
+        }
+
         builder(resolvedQualifier) {
             parents += abstractResolvedQualifierBuilder
             defaultFalse("isNullableLHSForCallableReference", "isFullyQualified")