Dashboard: Improve the appearance of "WordPress Events and News" dashboard...

Dashboard: Improve the appearance of "WordPress Events and News" dashboard widget for multi-day events.

If an upcoming event spans over several days, this information is now properly reflected in the widget.

Props imath, casiepa, iandunn, hareesh-pillai, melchoyce, mapk, desrosj, audrasjb, SergeyBiryukov.
Fixes #47798.
Built from https://develop.svn.wordpress.org/trunk@47124


git-svn-id: https://core.svn.wordpress.org/trunk@46924 1a063a9b-81f0-0310-95a4-ce76da25c4cd