Improves flow handling and adds runtime stats APIs

Refactors TCP and UDP flow managers to enhance analyzer selection and flow binding accuracy, including O(1) UDP stream rebinding by 5-tuple.
Introduces runtime stats tracking for engine and ruleset operations, exposing new APIs for granular performance and error metrics.
Optimizes GeoMatcher with result caching and supports efficient geosite set matching, reducing redundant computation in ruleset expressions.

ruleset/interface.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"net"
 	"strconv"
+	"sync/atomic"
 
 	"git.difuse.io/Difuse/Mellaris/analyzer"
 	"git.difuse.io/Difuse/Mellaris/modifier"
@@ -95,6 +96,28 @@ type Ruleset interface {
 	Match(StreamInfo) MatchResult
 }
 
+type Stats struct {
+	MatchCalls         uint64
+	MatchErrors        uint64
+	MatchLatencyNanos  uint64
+	LookupCalls        uint64
+	LookupErrors       uint64
+	LookupLatencyNanos uint64
+}
+
+type statsCounters struct {
+	MatchCalls         atomic.Uint64
+	MatchErrors        atomic.Uint64
+	MatchLatencyNanos  atomic.Uint64
+	LookupCalls        atomic.Uint64
+	LookupErrors       atomic.Uint64
+	LookupLatencyNanos atomic.Uint64
+}
+
+type StatsProvider interface {
+	Stats() Stats
+}
+
 // Logger is the logging interface for the ruleset.
 type Logger interface {
 	Log(info StreamInfo, name string)