[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/testData/cli/js/sourceMapEmbedSources.args

@@ -1,4 +1,5 @@
 $TESTDATA_DIR$/sourceMap.kt
+-Xlegacy-deprecated-no-warn
 -source-map
 -source-map-prefix
 ./