feat: add logc package, support AddGlobalFields for both logc and logx. (#2463)

* feat: add logc package

* feat: add logc, add AddGlobalFields for both logc and logx

* chore: add benchmarks

* chore: add more tests

* chore: simplify globalFields in logx

* chore: remove outdated comments

core/logx/writer.go

@@ -263,7 +263,18 @@ func buildFields(fields ...LogField) []string {
 	return items
 }
 
+func combineGlobalFields(fields []LogField) []LogField {
+	globals := globalFields.Load()
+	if globals == nil {
+		return fields
+	}
+
+	return append(globals.([]LogField), fields...)
+}
+
 func output(writer io.Writer, level string, val interface{}, fields ...LogField) {
+	fields = combineGlobalFields(fields)
+
 	switch atomic.LoadUint32(&encoding) {
 	case plainEncodingType:
 		writePlainAny(writer, level, val, buildFields(fields...)...)