Multiple web client connections created instead of utilizing existing initial connection

### Questions

If we set the server to a larger number of max concurrent threads like 250 streams, and only send 100 requests on the webclient, which is using a max pool size of 8, it seems that 8 connections are created instead of using the single connection for all the streams.

### Version

3.9.1

### Context
See reproducer

### Do you have a reproducer?

A reproducer is a simple project hosted on GitHub (or another forge supporting git clone operation) that has a build file that can be executed to reproduce the issue.

Reproducers are very helpful for contributors and will likely help them fixing your bug faster.

https://github.com/pantinor/vertx.issues/blob/main/issues/src/test/java/vertx/demo/StreamsVertxOnlyTest.java

### Steps to reproduce

Run the test above, note the failure on the assertion for expecting 1 connection instead of 8.

### Extra

* Anything that can be relevant such as OS version, JVM version