Add option to specify config in All-Projects

Now it is possible to change configuration of rate limiter in
All-Projects configuration.

Rate-limiter would only apply configuration from the All-Projects, if
gerrit is not replica.

To change configuration of rate limiter one needs to add
rate-limiter.config file to All-Projects refs/meta/config. If there is
no rate-limiter.config in All-Projects then the configuration would be
taken from etc/rate-limiter.config.

If the  rate-limiter configuration changed, then it would only affect users
whose permits were changed. If the permit of the user did not change
then the rate limit would stay. In case permit was changed then rate-limit
of the user would be deleted.

Feature: Issue 10306
Change-Id: Ie412837fb23d9c5c7e27e9edf5c0f92cf864ae57
8 files changed