stats: name lookups occur on every new http1 connection may cause contention #11069
Description
It appears that the h1 codec instantiates new stats every time it's instantiated:
#define ALL_HTTP1_CODEC_STATS(COUNTER) \
COUNTER(dropped_headers_with_underscores) \
COUNTER(metadata_not_supported_error) \
COUNTER(requests_rejected_with_underscores_in_headers) \
COUNTER(response_flood)
and those may induce symbol-table contention. It'd be good to pre-symbolize those at startup.