Envoy: Make xDS request timeout configurable

[rshriram]

Async Client uses NullRetryPolicy and the API fetcher hardcodes the upstream request timeout to 1s. This is too low in some environments, and it would be nice to make this configurable.
(https://github.com/envoyproxy/envoy/blob/master/source/common/http/rest_api_fetcher.cc#L56)

[rshriram]

please assign this to me

[jinuxstyle]

Is there any progress on this? @rshriram

[stale[bot]]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or other activity occurs. Thank you for your contributions.