Misleading warning for qos overwrites starting with **/

[Hugal31]

Describe the bug

When writing a QoS overwrite with a key expression starting with **/, PublisherBuilder::apply_qos_overwrites emits the following warning:

WARN main ThreadId(01) zenoh::api::builders::publisher: Publisher declared on `demo/example/zenoh-rs-pub` which is included by multiple key_exprs in qos config. Using qos config for `**/demo/**`

This is misleading, as after inspection, the only other "overwrite" is actually an empty overwrite for the ** key. I may be wrong but I believe this is due to the tree nature of the publisher_qos_tree.

A way to only emit this warning when relevant would be to filter on nodes with a non empty QoS ovewrite. I can make a PR for that.

P.S.: I have noticed when there are actually multiple overwrite, the one applied can vary between launches.

To reproduce

Start the z_pub example with the following configuration:

{
  qos: {
    publication: [
      {
        key_exprs: ["**/demo/**"],
        config: {
          priority: "data_high",
        },
      },
    ],
  },
}

System info

• Platform: Archlinux
• Zenoh 2311334