[JS SCRIPT] refactor js script infrastructure

- Implement proper script compiler proxy to correctly handle script and its closed-world dependencies
 - Clean up zoo of JsScriptCompilers

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt

@@ -44,7 +44,7 @@ class JsIrBackendContext(
     val symbolTable: SymbolTable,
     irModuleFragment: IrModuleFragment,
     val additionalExportedDeclarations: Set<FqName>,
-    override val configuration: CompilerConfiguration,
+    override val configuration: CompilerConfiguration, // TODO: remove configuration from backend context
     override val scriptMode: Boolean = false
 ) : CommonBackendContext {
     override val transformedFunction = mutableMapOf<IrFunctionSymbol, IrSimpleFunctionSymbol>()

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt

@@ -86,7 +86,7 @@ fun compile(
     return transformer.generateModule(moduleFragment)
 }
 
-fun compileForRepl(
+fun generateJsCode(
     context: JsIrBackendContext,
     moduleFragment: IrModuleFragment,
     nameTables: NameTables