Commit Message:
This PR fixes an SRDS crash when a scoped route uses inline route_configuration instead of route_configuration_name.

Additional Description:
When a scoped route uses inline route_configuration instead of route_configuration_name, the scope is added to scope_name_by_hash_ but not to route_provider_by_scope_ (no RDS provider is needed). If the on-demand route update path (onDemandRdsUpdate) is triggered for such a scope, route_provider_by_scope_[scope_name] inserts a null unique_ptr via operator[] and then dereferences it, causing a crash.

Use find() instead of operator[] to look up the scope in route_provider_by_scope_. If the scope has no RDS provider (inline config), return false to the callback instead of crashing.

Risk Level:
Low

Testing:
Unit test added

Signed-off-by: Xin Li lixinusa2013@gmail.com

Request variables

Key	Value
ref	6dafd4c
sha	1929540
pr	44071
base-sha	e980367
actor	@whutwhu
message	router/scoped_rds: guard on-demand update for inline-config scopes...
started	1774200297.712007
target-branch	main
trusted	false

Container image/s (as used in this CI run)

Envoy version (as used in this CI run)