[WIP]Support Gauge in access_loggers.stats

[TAOXUY]

Commit Message: add gauge support in access_loggers.stats Risk Level:low Testing:both unit test and integration test are added Docs Changes: updated in the protobuf comments Release Notes: updated Platform Specific Features:no

[repokitteh-read-only[bot]]

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/). envoyproxy/api-shepherds assignee is @mattklein123 CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/42226 was opened by TAOXUY.

see: more, trace.

[TAOXUY]

@kyessenov