Improve logger Pause handling (#24946)

The old EventWriter's Run does: 

```go
for {
    handlePause()
    select {
    case event <- Queue:
         write the log event ...
    }
}
```

So, if an event writer is started before the logger is paused, there is
a chance that the logger isn't paused for the first message.

The new logic is:

```go
for {
    select {
    case event <- Queue:
         handlePause()
         write the log event ...
    }
}
```

Then the event writer can be correctly paused

Author: wxiaoguang

modules/log/event_writer_base.go

@@ -68,18 +68,16 @@ func (b *EventWriterBaseImpl) Run(ctx context.Context) {
 		}
 	}
 
-	for {
-		if b.GetPauseChan != nil {
-			pause := b.GetPauseChan()
-			if pause != nil {
-				select {
-				case <-pause:
-				case <-ctx.Done():
-					return
-				}
+	handlePaused := func() {
+		if pause := b.GetPauseChan(); pause != nil {
+			select {
+			case <-pause:
+			case <-ctx.Done():
 			}
 		}
+	}
 
+	for {
 		select {
 		case <-ctx.Done():
 			return
@@ -88,6 +86,8 @@ func (b *EventWriterBaseImpl) Run(ctx context.Context) {
 				return
 			}
 
+			handlePaused()
+
 			if exprRegexp != nil {
 				fileLineCaller := fmt.Sprintf("%s:%d:%s", event.Origin.Filename, event.Origin.Line, event.Origin.Caller)
 				matched := exprRegexp.Match([]byte(fileLineCaller)) || exprRegexp.Match([]byte(event.Origin.MsgSimpleText))