api: Add total_issued_requests to Upstream Locality and Endpoint Stats. (#6692)
api: Add total_issued_requests to Upstream Locality and Endpoint Stats. (#6692)

total_issued_requests field tracks the count of requests issued since
the last report. This field will be used for global load balancing
decisions.

Envoy maintains a stats counter rq_total to track total
requests made. By latching this counter when load reporting period
begins, we are able to count the total requests issued in a load
reporting interval. This information is then used to populate the field
total_issued_requests.

Risk Level: Low
Testing: //test/integration:load_stats_reporter passes.

Signed-off-by: Karthik Reddy <rekarthik@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ cdddf54e8548036703ee928335a44c3b503b988b

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