Refactor script infrastructure for easier usage and testability:

- add script annotation for specifying default configuration for a script
- add support for this annotation in the default configurator
- rename configurator accordingly
- add default implementation of the refineConfiguration method
- make property bag class open

libraries/scripting/common/src/kotlin/script/experimental/api/scriptConfiguration.kt

@@ -25,6 +25,7 @@ interface ScriptCompilationConfigurator {
         scriptSource: ScriptSource,
         configuration: ScriptCompileConfiguration,
         processedScriptData: ProcessedScriptData = ProcessedScriptData()
-    ): ResultWithDiagnostics<ScriptCompileConfiguration>
+    ): ResultWithDiagnostics<ScriptCompileConfiguration> =
+        defaultConfiguration.asSuccess()
 }