Reland "[CrOS Hotspot] Add hotspot detailed view controller"

This is a reland of commit bd5e53ca
The HotspotDetailedViewControllerTest in the original CL triggers a
memory leak issue where the extra_icon_ in the HotspotDetailedView is
not released correctly. The fix is to set the icon's visibility instead
of trying to remove the extra_icon.
Uploaded patch#1 as the original CL and made the fix in patch#2 for easy
readability.

Bug: b/274154971
Change-Id: I3a234b41163d5315daccf4d61d0eb9da2b779fe2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4549240


Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Jason Zhang <jiajunz@google.com>
Cr-Commit-Position: refs/heads/main@{#1146720}