fix(dynamic_log_level): not work for nginx debug log

[chobits]

DESCRIPTION

When we use this api to modify log level to debug, nginx debug log does not output. The lua debug log works as expected.

CHANGELOG

• 1. return NGX_LOG_DEBUG_ALL to nginx-log-patch, and returnn log_level number to ffi upper user
• 2. add test case

ISSUE

fix KAG-2644

[CLAassistant]

All committers have signed the CLA.

[chobits]

For reviewers, we need to adhere nginx conventions here. like the nginx magic, note taht NGX_LOG_DEBUG_ALL is numerically greater than NGX_LOG_DEBUG. This numeric relationship is crucial for the functioning of all code segments that involve log->log_level comparison in Nginx.

// src/core/ngx_log.c

ngx_http_core_error_log
 -> ngx_log_set_log
   -> ngx_log_set_levels
     
static char *
ngx_log_set_levels(ngx_conf_t *cf, ngx_log_t *log)
{
+-- 52 lines: ngx_uint_t   i, n, d, found;----------------------------------------------------------------------------
    if (log->log_level == NGX_LOG_DEBUG) {
        log->log_level = NGX_LOG_DEBUG_ALL;
    }

    return NGX_CONF_OK;
}

[chobits]

For the caller using ffi call, we need to translate it from 0x7fff fff0 to log level number 0~8.

[chobits]

Do not merge this PR until we have released 3.5. We should make sure that kong 3.5 is stable and reliable.