Improve class name generation for scripts and REPL snippets

- allow to override default name/scheme
- implement host/engine specific names for jsr223 to avoid classloading
  clashes (also fix "eval in eval" test)

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

@@ -8,6 +8,7 @@ package kotlin.script.experimental.api
 import java.io.Serializable
 import kotlin.script.experimental.util.PropertiesCollection
 
+// Warning: during the transition to the new REPL infrastructure, should be kept in sync with REPL_CODE_LINE_FIRST_NO/REPL_CODE_LINE_FIRST_GEN
 const val REPL_SNIPPET_FIRST_NO = 1
 const val REPL_SNIPPET_FIRST_GEN = 1
 
@@ -48,3 +49,17 @@ val ScriptCompilationConfigurationKeys.repl
  */
 val ReplScriptCompilationConfigurationKeys.resultFieldPrefix by PropertiesCollection.key<String>("res")
 
+typealias MakeSnippetIdentifier = (ScriptCompilationConfiguration, ReplSnippetId) -> String
+
+/**
+ * The REPL snippet class identifier generation function
+ */
+val ReplScriptCompilationConfigurationKeys.makeSnippetIdentifier by PropertiesCollection.key<MakeSnippetIdentifier>(
+    { _, snippetId ->
+        makeDefaultSnippetIdentifier(snippetId)
+    })
+
+fun makeDefaultSnippetIdentifier(snippetId: ReplSnippetId) =
+    "Line_${snippetId.no}${if (snippetId.generation > REPL_SNIPPET_FIRST_GEN) "_gen_${snippetId.generation}" else ""}"
+
+

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

@@ -57,6 +57,11 @@ fun ScriptCompilationConfiguration?.with(body: ScriptCompilationConfiguration.Bu
  */
 val ScriptCompilationConfigurationKeys.displayName by PropertiesCollection.key<String>()
 
+/**
+ * The default script class name
+ */
+val ScriptCompilationConfigurationKeys.defaultIdentifier by PropertiesCollection.key<String>("Script")
+
 /**
  * The script filename extension
  * Used for the primary script definition selection as well as to assign a kotlin-specific file type to the files with the extension in Intellij IDEA