[Gradle, JS] IR by default and report warnings for using legacy compiler

- just legacy - report warning about deprecation
- both - report warning about deprecation of legacy
- no compiler explicitly chosen - error about explicit setting compiler

warn from cli legacy compiler

nowarn flag - kotlin.js.compiler.nowarn

KT-42326
KT-53074

compiler/tests-common/tests/org/jetbrains/kotlin/jvm/compiler/AbstractKotlinCompilerIntegrationTest.kt

@@ -162,6 +162,7 @@ abstract class AbstractKotlinCompilerIntegrationTest : TestCaseWithTmpdir() {
                 args.add("-libraries")
                 args.add(classpath.joinToString(File.pathSeparator))
             }
+            args.add("-Xlegacy-deprecated-no-warn")
             args.add("-output")
             args.add(output.path)
             args.add("-meta-info")