Make use of real-time updates for new short URLs

[acelaya]

Summary

Shlink 3.2 introduced the "new short URL" real-time update. Use it in the next scenarios:

• Overview page. Total short URLs counter.
• Overview page. Last 5 short URLs (prepend and drop last one when there's 5 or more).
• Short URLs list. Counter, when new short URL fulfills active filter.
• Short URLs list. Prepend to list if new short URL should be displayed in active page (this one is tricky, as determining that requires computing active ordering, active filter and active page).