[Bug]: js_test chdir fails on windows as bazel starts test in runfiles

### What happened?

Whilst trying to enable this test for windows: https://github.com/aspect-build/rules_js/blob/715f9abbdcde3b9e18679ab52b3c36b4c71e5856/js/private/test/data/BUILD.bazel#L112

I've noticed that the chdir fails:
```
==================== Test output for //js/private/test/data:from-genrule-data:
DEBUG: aspect_rules_js[js_test]: changing directory to user specified package js/private/test/data
D:/udu/b/j6bnscvo/execroot/_main/bazel-out/x64_windows-fastbuild/bin/js/private/test/data/from-genrule-data_/from-genrule-data: line 455: cd: js/private/test/data: No such file or directory
DEBUG: aspect_rules_js[js_test]: exit code: 1
================================================================================
```

The js_test is reaching this block; indicating that the test has been started in runfiles: https://github.com/aspect-build/rules_js/blob/715f9abbdcde3b9e18679ab52b3c36b4c71e5856/js/private/js_binary.sh.tpl#L181

Thus the code does not cd to root of output directory and the chdir later fails.

I'm happy to fix this as part of my Windows work if someone can let me know what the correct behaviour should be.

### Version

Latest rules_js
Windows

### How to reproduce

```shell

```

### Any other information?

_No response_

Start with js/private/test/data/BUILD.bazel and the js_test path, then read the runfiles handling around the referenced block in js/private/js_binary.sh.tpl on Windows. Reproduce the from-genrule-data failure and establish the expected working directory before determining what successful chdir behavior should be.

Written by the indexing model from the issue text.