feat(GlTruncate): add slots to surround the text

mentioned in commit 15b4ccbf

mentioned in merge request gitlab!82590 (closed)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2746 (closed)

mentioned in merge request status-page!476 (merged)

mentioned in merge request gitlab!83216 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2755 (merged)

mentioned in merge request gitlab-docs!2518 (merged)

mentioned in merge request gitlab-docs!2519 (merged)

mentioned in merge request gitlab-docs!2520 (closed)