Update Stylelint formatter for Stylelint 16
Problem/Motivation
In core, Stylelint is now on version 16 since #3488005: Update stylelint* to latest releases
Stylelint 16 uses ESM and promises; this breaks the Stylelint formatter that core previously used (leon0399/stylelint-formatter-gitlab), this was swapped out for a better formatter in #3467309: Replace abandoned, not working with latest stylelint, leon0399/stylelint-formatter-gitlab with gitlab-formatters/stylelint-formatter-gitlab
This also appears to break the JUnit formatter that this project uses.
Steps to reproduce
https://git.drupalcode.org/project/experience_builder/-/jobs/3618049
Proposed resolution
Swap stylelint-junit-formatter for gitlab-formatters/stylelint-formatter-gitlab.
Output native GitLab format results instead of JUnit.
Remaining tasks
User interface changes
API changes
Data model changes
Related issue: Issue #3488005
Related issue: Issue #3467309
Related issue: Issue #3494820