Propagate `iceberg.hadoop.conf.` prefixed properties to `HadoopFileIO`'s Configuration

### Feature Request / Improvement

### Description

`HadoopFileIO` is configurable via two paths:
1. `FileIO.initialize(Map)` — the catalog pushes catalog properties in.
2. `HadoopConfigurable#setConf(Configuration)` — a caller-supplied Hadoop `Configuration`.

Today, **catalog properties are never propagated into the Hadoop Configuration that `HadoopFileIO` uses for its `FileSystem` lookups.** If a user wants to parameterize Hadoop-level settings (`fs.s3a.endpoint`, `fs.s3a.path.style.access`, `fs.defaultFS`,
`fs.s3a.access.key`, `fs.azure.account.key.*`, etc.) on a per-catalog basis, their options today are:

- Mutate the shared `Configuration` object out-of-band before creating the catalog. This leaks settings across catalogs that share the same `Configuration`, and is impossible in environments like Flink session clusters where the same `Configuration` is reused for many catalogs.
- Carry a separate `hadoop-site.xml` per deployment. Doesn't compose with REST-catalog deployments where the catalog is discovered dynamically.
- Implement a custom `FileIO`. Overkill for a configuration-only concern.
### Proposed solution

Treat catalog properties whose key starts with **`iceberg.hadoop.conf.`** as Hadoop Configuration overrides: strip the prefix and `set(...)` them on the `Configuration` that `HadoopFileIO` uses. Apply the override on both `initialize(...)` and `setConf(...)` so the feature works whether the catalog driver or a Hadoop-aware caller is in charge of the configuration.

To avoid mutating caller-owned objects, copy the base `Configuration` before overlaying:

```java
private static final String HADOOP_CONF_PREFIX = "iceberg.hadoop.conf.";

@Override
public void initialize(Map props) {
this.properties = SerializableMap.copyOf(props);
rebuildConfWithProperties(getConf());
}

@Override
public void setConf(Configuration conf) {
rebuildConfWithProperties(conf);
}

private void rebuildConfWithProperties(Configuration baseConf) {
Configuration conf = new Configuration(baseConf);
PropertyUtil.propertiesWithPrefix(properties, HADOOP_CONF_PREFIX).forEach(conf::set);
this.hadoopConf = new SerializableConfiguration(conf);
}
```

### Example usage

```properties
# REST catalog config, or any Iceberg catalog config
iceberg.hadoop.conf.fs.s3a.endpoint = https://s3.eu-west-1.example.com
iceberg.hadoop.conf.fs.s3a.path.style.access = true
iceberg.hadoop.conf.fs.s3a.connection.maximum = 200
```

### Query engine

None

### Willingness to contribute

- [x] I can contribute this improvement/feature independently
- [ ] I would be willing to contribute this improvement/feature with guidance from the Iceberg community
- [ ] I cannot contribute this improvement/feature at this time