Add support for `group(<fieldName>)-description`,
`group(<fieldName>)-label`, `group(<fieldName>)-label-description`,
and `after(<fieldName>)` slots

feat(GlFormFields): add support for additional slots

See merge request gitlab-org/gitlab-ui!3982



Merged-by: Paul Slaughter <pslaughter@gitlab.com>
Approved-by: Andrew Fontaine <afontaine@gitlab.com>
Approved-by: Chris Micek <cmicek@gitlab.com>
Approved-by: Chad Lavimoniere <clavimoniere@gitlab.com>
Approved-by: Paul Slaughter <pslaughter@gitlab.com>
Reviewed-by: Andrew Fontaine <afontaine@gitlab.com>
Co-authored-by: Peter Hegman <phegman@gitlab.com>

# [78.8.0](gitlab-org/gitlab-ui@v78.7.0...v78.8.0) (2024-04-04)

### Features

* **GlFormFields:** add support for additional slots ([6ff8a22a](gitlab-org/gitlab-ui@6ff8a22a))