[Enhancement] Add a property to configure Client/Master RMI hostname to prevent callback failures caused by VPN/Virtual fake IPs

**Relates to closed issue:**[#1830: JMeter server doesn't alert the user when the host is defined as a loopback address](https://github.com/apache/jmeter/issues/1830)

#### 1. Description of the Problem
While Issue #1830 successfully addressed the problem of the loopback address (`127.0.0.1`), modern networking environments (with VPNs, proxy software like Clash/Surge in TUN mode, Docker, and Virtual Machines) introduce a new, very common issue: **Fake/Virtual IPs**.

Currently, when starting a distributed test, the `ClientJMeterEngine` (Master/Controller) relies on `InetAddress.getLocalHost()` to determine its own IP address to embed into the RMI stub. However, `getLocalHost()` frequently picks up the highest-priority virtual network interface created by VPNs (resulting in fake IPs like `2.0.1.4` or `198.18.0.1`).

**The consequence:**
1. The Master sends the test script along with this "fake IP" stub to the remote `jmeter-server` (Slave).
2. The Slave finishes the test and attempts to return the results to the Master by connecting to this fake IP.
3. The connection times out (`java.rmi.ConnectException: Connection refused to host: 2.0.1.4; nested exception is: java.net.ConnectException: Operation timed out`).
4. The Master never receives the test results, and the test hangs or fails silently on the client side.

#### 2. Proposed Solution / Enhancement
Introduce a dedicated JMeter configuration property in `jmeter.properties` to explicitly define the callback IP for the Master/Client.

**Example addition to `jmeter.properties`:**
```properties
# Set the IP address or hostname for the Master to receive results from remote servers.
# If not set, JMeter will default to InetAddress.getLocalHost()
#client.rmi.hostname=192.168.1.50
```

**Implementation Idea:**
During the early initialization phase of JMeter (before `ClientJMeterEngine` starts the RMI registry/exports the object), JMeter could read `client.rmi.hostname` from `jmeter.properties`. If configured, JMeter explicitly sets the JVM system property programmatically:

#### 3. Expected Benefit
This would greatly improve the user experience for distributed testing. Users would no longer need to battle with undocumented CLI arguments or disable their VPNs/virtual adapters just to run a remote JMeter test. All RMI configurations (ports and hosts) would be centralized within `jmeter.properties`.

### Actual behavior

_No response_

### Steps to reproduce the problem

can't not set current

### JMeter Version

5.6.3

### Java Version

_No response_

### OS Version

_No response_