config: implement discovery request rate limiting (#4787)
config: implement discovery request rate limiting (#4787)

Implements rate limiting for discovery requests

Risk Level: Medium. This changes the way DiscoveryRequests are processed today (queues them) and adds rate limiting behaviour. While we have good test coverage (and also additional tests have been added), there is some risk.
Testing: Automated tests
Docs Changes: N/A
Release Notes: Added

Fixes #4718

Signed-off-by: Rama <rama.rao@salesforce.com>

Mirrored from https://github.com/envoyproxy/envoy @ 455714694bb930729c32a1f92c0f9c4f083a3bdb

lyft/envoy-api,lyft/envoy-api,lyft/envoy-api