network: Add NetworkInfoBubble regression test

This change updates the existing NetworkDetailedView unit tests to use
the actual system tray instead of creating an instance of the
NetworkDetailedView so that the tests are executed in an environment
much more similar to production. These updates allow these tests to
become a regression test for the associated bug.

Bug: b/303382616, b/304840723
Test: Unit tests.
Change-Id: Iec3534767ba4c0d42a889c441b75e2cbe7c82235
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4932594
Reviewed-by: Jiaming Cheng <jiamingc@chromium.org>
Commit-Queue: Chad Duffin <chadduffin@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1212362}