feat: As a user, I want apisix to warn me if I have multiple routes that would match for the same URI

### Description

Example:

Route one:

```bash
curl -XPUT 127.0.0.1:9180/apisix/admin/routes/1 -H "X-API-KEY: edd1c9f034335f136f87ad84b625c8f1" -d '{
"uri":"/anything/*",
"plugins": {
.....
},
"upstream":{
"type":"roundrobin",
"nodes":{
"httpbin.org:80":1
}
}
}'
```

route two:

```bash
curl -XPUT 127.0.0.1:9180/apisix/admin/routes/2 -H "X-API-KEY: edd1c9f034335f136f87ad84b625c8f1" -d '{
"uri":"/anything/*",
"plugins": {
.....
},
"upstream":{
"type":"roundrobin",
"nodes":{
"abc.org:80":1
}
}
}'
```
As you can see both routes have same URI.
In this case, APISIX would randomly match any route when I visit `127.0.0.1:9080/anything/test`.

I understand that this is the user's fault but if users receive a warning when they try to create a route that has a conflicting URI it would lead to a better UX.

No files or tests are named in the issue. Start by tracing route creation and URI matching in APISIX, then determine how identical or overlapping URIs are detected; done means creating a conflicting route produces a clear warning without preventing the route from being created, with coverage for the example behavior.

Written by the indexing model from the issue text.