xds: introduce initial_fetch_timeout option to limit initialization time (#6048)
xds: introduce initial_fetch_timeout option to limit initialization time (#6048)

Introduce new optional configuration parameter initial_fetch_timeout to ConfigSource proto.
This parameter can be used to limit time Envoy spend on initialization of CDS, LDS and RDS.
Enabling this timeout prevents Envoy from being stuck in PRE_INITIALIZING or INITIALIZING phase, as described in #5862.

Risk Level: Low (optional feature, disabled by default)
Testing: manual testing, unit tests
Docs Changes: add new parameter initial_fetch_timeout to ConfigSource proto
Release Notes: Added

Fixes #5862

Signed-off-by: Marcin Falkowski <marcin.falkowski@allegro.pl>

Mirrored from https://github.com/envoyproxy/envoy @ 06576443805cc651a8b404da995aa26f9a8720f5

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