[DBSC] Wait for all controllers before resuming throttled requests

When a request is throttled, BoundSessionCookieRefreshServiceImpl
informs all controllers and waits for all of them to call "resume"
before releasing the request.

This requires combining ResumeBlockedRequestsTriggers from each
controller into one value for metrics reporting. We could have
propagated multiple values to the caller but we want to record the
histogram only once per request, so it's simpler to aggregate triggers
immediately.

The implementation in this CL is incomplete not all of the controllers
might be relevant for a request. Picking the right set of controller is
left for follow-up CLs. Since the current impl is restricted to only one
session, the intermediate solution shouldn't have any impact.

Bug: b/325450696
Change-Id: I4e40d30efac1993fbede735a63e369477891609e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5588628


Commit-Queue: Monica Basta <msalama@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Alex Ilin <alexilin@chromium.org>
Reviewed-by: Monica Basta <msalama@chromium.org>
Auto-Submit: Alex Ilin <alexilin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312681}