Added channel timeout configurations for REST WebClient provider

Editor assessment

The subject states the addition concretely: channel timeout configurations are added for the REST WebClient provider. The component and the tunable are both named, so operators know what they can now adjust. The fix type is defensible for closing a robustness gap even though feat would fit; the rubric tolerates straddling choices. No scope or body is present, and neither is demanded for a configuration addition. Style is clean apart from the past-tense verb: no junk, no trailing period. Good and publishable.