Widen metrics period selector

[arjunkomath]

Summary

• increase the metrics period selector trigger and menu width
• prevent selected period labels from wrapping
• keep the label and chevron consistently spaced

Validation

• npx biome check components/service/details/service-metrics-page.tsx
• npx tsc --noEmit
• git diff --check

[github-actions]

React Doctor found no new issues. 🎉

_{Reviewed by React Doctor for commit 7821406.}