Fix io.netty security vuln from azure module

# What is currently missing?

We notice that the hadoop modules explicitly exclude `netty.io` modules here: https://github.com/Aiven-Open/tiered-storage-for-apache-kafka/blob/ecfa17e445e98d6f66209cb556188e195053f334/core/build.gradle#L111

However, netty is still pulled transitively via azure-core-http-netty and reactor-netty in the storage/azure module. Netty 4.1.108.Final is causing some security tickets to trigger on our kafka nodes. We need `4.1.136.Final` or higher to patch the security concern.

# How could this be improved?

In the root build.gradle, we could add a `resolutionStrategy` like so:
```
configurations.all {
resolutionStrategy.eachDependency { details ->
if (details.requested.group == 'io.netty') {
details.useVersion nettyVersion
details.because 'CVE-2026-59921, CVE-2026-41417 and others require >= 4.1.136.Final'
}
}
```
With a nettyVersion param.

I'm assuming we can't add a `exclude group: "io.netty"` statement for azure-blob package, because it is required for that package, unlike hadoop.

# Is this a feature you would work on yourself?

I could open an upstream PR for whichever approach we think is best.

* [ ] I plan to open a pull request for this feature