CSF-tools: Fix ConfigFile string literal property handling

[yannbf]

Issue: N/A

What I did

I noticed that some automigrations were failing in the sandboxes repo (yay automigration.log file), and the reason is that the generated main.js contains a format which was unsupported in the new getNameFromPath function in csf-tools. This PR fixes that.

How to test

This is covered in unit tests, but feel free to compile CLI and run sb automigrate in a sandbox

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[shilman]

LGTM. Great catch!