Http Max Connection Duration Jitter

Added :ref:max_connection_duration_jitter <envoy_v3_api_field_config.core.v3.HttpProtocolOptions.max_connection_duration_jitter> to HttpProtocolOptions. When set, the max_connection_duration timer is extended by a random amount up to max_connection_duration * jitter / 100, preventing a thundering-herd of reconnects when many connections are established at roughly the same time. This follows the same pattern as TCP proxy's max_downstream_connection_duration_jitter_percentage.