Move output-check-only report adjustments to interop unit tests

Instead of adjusting report bodies in the interop runner itself, we
perform them in the unit tests. This will allow other code, e.g. an
independent test-output checker, to use the runner without adjustments.

For now we pass the Aggregation Service public key as a parameter to
the runner while we determine the best way to allow tests themselves
to cover the key/encryption behavior.

This change also fixes a bug in which verbose debug reports containing
entire event-level report bodies were not adjusted properly with
respect to their randomized_trigger_rate field.

Change-Id: I57662025b9484feec6ab0b76eb6dccb745dcbe6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5415013


Commit-Queue: Andrew Paseltiner <apaseltiner@chromium.org>
Reviewed-by: Nan Lin <linnan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1281834}