[AA] Add symbol tests for symbols from JS klibs

Use test compiler runner to compile JS libraries. Determine compiler
by the specified TARGET_PLATFORM. Add tests for dynamic type and
JS-specific .proto extensions.

Refactor the code for mock library compilation to make the switch
between platforms more straightforward.

KTIJ-27566
KT-63217

compiler/tests-compiler-utils/tests/org/jetbrains/kotlin/test/MockLibraryUtil.kt

@@ -163,7 +163,7 @@ object MockLibraryUtil {
         runCompiler(compiler2JVMClass, args)
     }
 
-    private fun runJsCompiler(args: List<String>) {
+    fun runJsCompiler(args: List<String>) {
         runCompiler(compiler2JSClass, args)
     }