[Task][Performance] Reduce routine matching and configuration-sync log volume #7643

Performance baseline and program tracking: #7650.

Goal

Reduce avoidable diagnostic logging in request matching and large configuration synchronization. Suggested sequence: first implementation batch.

Current evidence

At the reviewed commit, AbstractShenyuPlugin.defaultMatchSelector/defaultMatchRule emits INFO success messages on the default matching path, independently of the explicit per-selector/per-rule success-log flags. Bootstrap disables matching-result caches by default. ShenyuWebsocketClient.handleResult logs the complete received payload at INFO. Existing Logback configurations already use async appenders; adding another async appender is not the objective.

Source at reviewed commit

Scope and acceptance criteria

• Gate routine match-success diagnostics behind DEBUG or the explicit matching-log setting; document the choice without duplicating messages.
• Log configuration event metadata/count/size rather than full payloads at INFO; retain actionable failures and required audit records.
• Regression tests cover disabled/enabled matching logs and unchanged routing results.
• Compare fixed-load log bytes/sec, allocation rate, CPU and p99 before/after with identical logging destinations.
• Report observed results and any diagnostic tradeoff. No performance improvement percentage is assumed before measurement.