Dynamic Modules Added Config Load Error Stats All Extensions

Dynamic module extensions now emit counters when loading their configuration fails, so that failures (which are otherwise either only surfaced to the control plane or, for the HTTP filter's remote fetch path, silently fail open) are observable. The counters are emitted on the server-wide stats scope under the dynamic_modules. prefix (the server scope is used so the counters survive a rejected listener configuration update): module_load_error (the module could not be loaded — missing/invalid source, dlopen failure, by-name lookup miss, or a required ABI symbol could not be resolved), config_init_error (the module loaded but initializing the in-module configuration failed, e.g. on_*_config_new returned null), remote_fetch_error (a remote module source failed to fetch or load, including NACK-mode cache misses; HTTP filter only) and per_route_config_error (a per-route configuration failed to load; HTTP filter only). Each counter carries a config_name tag set to the configured name of the extension instance — for example filter_name, transport_socket_name, lb_policy_name, tracer_name or cluster_name (falling back to default when the extension has no per-instance name, as for the UDP listener filter) — so failures can be attributed to a specific extension instance. The upstreams/http bridge is not yet instrumented because its module is loaded lazily on the data path where no server-wide stats scope is available.