Replace shelljs in run-ci-javascript-tests.js (#52095)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/52095

This diff removes `shelljs` from `run-ci-javascript-tests.js` and replaces `echo, exec, and exit` methods.

### Motivation

Decrease number of references to `shelljs` across the react-native-github.

Changelog:
[Internal]

Reviewed By: NickGerleman

Differential Revision: D76512374

fbshipit-source-id: 6e02901b570cf9a36bd13a075106a7066a85a2d9