[JS IR] Perform optimizations on the generated JS code

The patch adopts and reuses the optimizations from the legacy backend.

The optimizations remove useless temporary variables,
statements and simplify generated JS code.

The optimizations can be disabled by `-Xoptimize-generated-js=false`.

Related to KT-51139

compiler/cli/cli-common/gen/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArgumentsCopyGenerated.kt

@@ -48,6 +48,7 @@ fun copyK2JSCompilerArguments(from: K2JSCompilerArguments, to: K2JSCompilerArgum
     to.moduleKind = from.moduleKind
     to.moduleName = from.moduleName
     to.noStdlib = from.noStdlib
+    to.optimizeGeneratedJs = from.optimizeGeneratedJs
     to.outputDir = from.outputDir
     to.outputFile = from.outputFile
     to.outputPostfix = from.outputPostfix

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt

@@ -605,6 +605,16 @@ class K2JSCompilerArguments : CommonCompilerArguments() {
             field = value
         }
 
+    @Argument(
+        value = "-Xoptimize-generated-js",
+        description = "Perform additional optimizations on the generated JS code"
+    )
+    var optimizeGeneratedJs = true
+        set(value) {
+            checkFrozen()
+            field = value
+        }
+
     private fun MessageCollector.deprecationWarn(value: Boolean, defaultValue: Boolean, name: String) {
         if (value != defaultValue) {
             report(CompilerMessageSeverity.WARNING, "'$name' is deprecated and ignored, it will be removed in a future release")