[Wasm] Loader improvements

- Output ES modules instead of plain files
- Support -Xwasm-launcher=d8 for d8 shell used in tests and benchmarks.
- Reuse launcher generation logic in CLI and box tests runners.
- Create separate output directory for each box since
  there are multiple output files generated for each test.
- Stop using absolute paths in generate JS files
  to simplify running generated code on different machine
- Remove ">>>" from println output


Merge-request: KT-MR-5729
Merged-by: Svyatoslav Kuzmich <svyatoslav.kuzmich@jetbrains.com>

libraries/stdlib/wasm/src/kotlin/io.kt

@@ -7,11 +7,11 @@ package kotlin.io
 
 import kotlin.wasm.internal.*
 
-@JsFun("(error) => console.error(\">>>  \" + error)")
+@JsFun("(error) => console.error(error)")
 internal external fun printError(error: String?): Unit
 
-@JsFun("(message) => console.log(\">>>  \" + message)")
-private external fun printlnImpl(error: String?): Unit
+@JsFun("(message) => console.log(message)")
+private external fun printlnImpl(message: String?): Unit
 
 /** Prints the line separator to the standard output stream. */
 public actual fun println() {