
### Environment

* Dubbo version: 3.0.2.1
* Operating System version: Linux 4.14.152-127.182.amzn2.x86_64
* Java version: 1.8_310

### Steps to reproduce this issue

1. A provider annotated with @DubboService(tag = 'XXX')
2. A Consumer annotated with @DubboReference(tag = 'XXX')
3. Consumer will complain no provider found

Possible Cause:
1. TagDynamicStateRouter#line 112 will hardcode tag as 'noTag' even the service has a valid tag but without tagRouterRule set
```
invocation.setAttachment(TAG_KEY, NO_TAG);
```
2. TagStaticStateRouter#64 try to locate the tag with below code, however the tag attachment already set as noTag from previous router, hence the tag is always noTag even the url has a valid tag set.
```
 String tag = StringUtils.isEmpty(invocation.getAttachment(TAG_KEY)) ? url.getParameter(TAG_KEY) :
            invocation.getAttachment(TAG_KEY);
        if (StringUtils.isEmpty(tag)) {
            tag = NO_TAG;
        }
```

Possible Fix:
replace StringUtils.isEmpty as below function:
```
boolean isNoTag(String value) {
      return StringUtils.isEmpty(value) || NO_TAG.equals(value));
}
```
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package org.apache.dubbo.rpc.cluster.router.tag;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.apache.dubbo.common.URL;
import org.apache.dubbo.common.utils.CollectionUtils;
import org.apache.dubbo.common.utils.StringUtils;
import org.apache.dubbo.rpc.Invocation;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.RpcException;