Fix: update oncall rotation name to truncate

What does this MR do?

A tiny MVC for: #324714 (closed) where we truncate long rotation names and add a supporting tool tip for hover.

How/What to test

This feature needs the minimal license is GitLab Premium 👀

To validate this merge:

• Navigate to Operations => On-call Schedules or direct link is your_project/-/oncall_schedules e.g. http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/oncall_schedules.
• Click "Add schedule on empty state"
• Add a base schedule
• Click "Add a rotation"
• Add a base rotation with a long name
• Verify the new rotation name is truncate and has a tooltip for hover

Screenshots (strongly suggested)

Before	After

Does this MR meet the acceptance criteria?

Conformity

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Related to #324714 (closed)