Reland "Drop psm::FakeRlweClient"

This is a reland of commit b53d2867c3db9e63534ef989afaa422d87958eb5

Original change's description:
> Drop psm::FakeRlweClient
>
> FakeRlweClient is anything but simple. It partially reimplements the
> PIR logic from the
> private_membership::rlwe::PrivateMembershipRlweClient, which forces
> the policy::RequestHandlerForPsmAutoEnrollment to reply with
> corresponding data. However, all of this should be implementation
> details of the PSM library. It contradicts the general idea that
> tests should be easy to understand.
>
> This change drops the FakeRlweClient and the
> RequestHandlerForPsmAutoEnrollment.
>
> Instead, tests can now use psm::RlweTestSupport to construct an
> RlweClientImpl from a test case from the PSM library's test database.
> The EmbeddedPolicyTestServer is also using the test cases from the
> test database to validate requests and send appropriate responses.
>
> This makes the test logic less complex, requiring less understanding
> of implementation details.
>
> Bug: b/241911665
> Change-Id: Ifae396257638433503ff82e19945e62d38df60c1
> Tests: Refactored browser tests
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4155468
> Reviewed-by: Danila Kuzmin <dkuzmin@google.com>
> Commit-Queue: Roland Bock <rbock@google.com>
> Reviewed-by: Igor <igorcov@chromium.org>
> Reviewed-by: Amr Aboelkher <amraboelkher@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1097319}

Bug: b/241911665
Change-Id: Id672d710fdd09c0131690a081b5dd0f1431fda9f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4200175
Reviewed-by: Amr Aboelkher <amraboelkher@chromium.org>
Reviewed-by: Sergiy Belozorov <sergiyb@chromium.org>
Commit-Queue: Roland Bock <rbock@google.com>
Reviewed-by: Igor <igorcov@chromium.org>
Reviewed-by: Danila Kuzmin <dkuzmin@google.com>
Cr-Commit-Position: refs/heads/main@{#1100454}
NOKEYCHECK=True
GitOrigin-RevId: 0b769cf276c1422923485fd0949257e3ef8ffd7d
1 file changed