message: stats: Fully-qualify stats macros
  Fully-qualify the expanded portions of stats macros for use in external callsites.
  Risk Level: Low.
diff: @@ -32,12 +32,13 @@ namespace Envoy {
  * MY_COOL_STATS(POOL_COUNTER(...), POOL_GAUGE(...), POOL_HISTOGRAM(...))};
  */
  -#define GENERATE_COUNTER_STRUCT(NAME) Stats::Counter& NAME##_;
  -#define GENERATE_GAUGE_STRUCT(NAME, MODE) Stats::Gauge& NAME##_;
  -#define GENERATE_HISTOGRAM_STRUCT(NAME) Stats::Histogram& NAME##_;
  +// Fully-qualified for use in external callsites.
  +#define GENERATE_COUNTER_STRUCT(NAME) Envoy::Stats::Counter& NAME##_;
  +#define GENERATE_GAUGE_STRUCT(NAME, MODE) Envoy::Stats::Gauge& NAME##_;
  +#define GENERATE_HISTOGRAM_STRUCT(NAME) Envoy::Stats::Histogram& NAME##_;
  #define FINISH_STAT_DECL_(X) + std::string(#X)),
  -#define FINISH_STAT_DECL_MODE_(X, MODE) + std::string(#X), Stats::Gauge::ImportMode::MODE),
  +#define FINISH_STAT_DECL_MODE_(X, MODE) + std::string(#X), Envoy::Stats::Gauge::ImportMode::MODE),
  #define POOL_COUNTER_PREFIX(POOL, PREFIX) (POOL).counter(PREFIX FINISH_STAT_DECL_
  #define POOL_GAUGE_PREFIX(POOL, PREFIX) (POOL).gauge(PREFIX FINISH_STAT_DECL_MODE_
  