Add test verifying subdomains of token origin can't disable TopLevelTpcd

While subdomain matching origin trial tokens can be used by subdomains
of the origin stored in the token (the "token origin") to enable a
trial, a document without the token present must be loaded from the
token origin itself in order to disable it.

The TopLevelTpcd deprecation (AKA reverse-origin) trial's state for a
given origin (and its subdomains) is mirrored in content settings,
introducing additional confusion. This CL adds a browser test to verify
that the behavior described above holds true for the TopLevelTpcd trial.

Bug: NONE
Change-Id: Ib3bbc66f9517d13fb14fd4320e635ccd5f8d59ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5347918
Reviewed-by: Anton Maliev <amaliev@chromium.org>
Commit-Queue: Joshua Hood <jdh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1269215}