[JS IR] Add to IR keep possibility similar to legacy-dce one

It helps to:

- keep declarations even if they are not reachable and not exported
- not minify names of not exported declarations

Compiler argument: -Xir-keep=A,B

Can be used for top-level declarations or for member

^KT-54118 fixed

compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt

@@ -100,6 +100,10 @@ class K2JsIrCompiler : CLICompiler<K2JSCompilerArguments>() {
                 module,
                 phaseConfig,
                 irFactory,
+                keep = arguments.irKeep?.split(",")
+                    ?.filterNot { it.isEmpty() }
+                    ?.toSet()
+                    ?: emptySet(),
                 dceRuntimeDiagnostic = RuntimeDiagnostic.resolve(
                     arguments.irDceRuntimeDiagnostic,
                     messageCollector