[NVS-httpcache] test the behavior on prerendering pages

This is a follow-up of I6d6a4f8d8dfb4855472a74059016a22b58491346 that
we need to test the prerender pages' behavior after enabling this
feature.

This CL also initializes last_error_time_ticks_ with TimeTicks::Min();
since the test suite may use the TimeTicks that starts from 0, it is
possible that
`last_error_time_ticks_ + SearchPrefetchErrorBackoffDuration` is
greater than the current timeticks for the first attempt, and that's why the test sometimes fails.

The value of TimeTicks::Min() (-inf) is reasonable to reflect the
fact that the SearchPrefetchService never fails before.

Bug: 388557183
Change-Id: I2293908b00c5c1fc9331c3021b02509e81407afc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6383241
Commit-Queue: Lingqi Chi <lingqi@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1440726}