edgeHub doesn't delete expired messages with RefCount > 0

## Expected Behavior
In case a custom module A is down (stopped, failed, hung, idle, whatever) and another custom module B sends messages to it, messages should be deleted from the edgeHub storage to prevent a full disk.

## Current Behavior
Even if the TTL is already expired, messages stay in the edgeHub storage.

## Steps to Reproduce
Provide a detailed set of steps to reproduce the bug.
1. having one module publishing a lot of messages to another module
2. let the other module crash always a few seconds after startup (after 20 times of retry, edgeAgent doesn't restart the module anymore)
3. check the size of the edgeHub storage directory

## Context (Environment)

### Output of `iotedge check`

Click here

```

independent

```

### Device Information
* Host OS [e.g. Ubuntu 22.04, Windows Server IoT 2019]: Ubuntu 22.04 and Debian 12
* Architecture [e.g. amd64, arm32, arm64]: amd64 and arm64
* Container OS [e.g. Linux containers, Windows containers]: Linux containers

### Runtime Versions
* aziot-edged [run `iotedge version`]: 1.5
* Edge Agent [image tag (e.g. 1.0.0)]: 1.5.19
* Edge Hub [image tag (e.g. 1.0.0)]: 1.5.19
* Docker/Moby [run `docker version`]: 20.10.11+azure-2

## Logs

there are already > 1 Mio messages in the edgeHub Rocks DB

```
edgehub_messages_sent_total{iothub="prodIotHubNtuity.azure-devices.net",edge_device="a17f9e19-1f4a-4168-8f56-2badb1a88646",instance_number="1b3417d6-ded1-4752-a57c-16765ff477d6",from="a17f9e19-1f4a-4168-8f56-2badb1a88646/Modbus",to="a17f9e19-1f4a-4168-8f56-2badb1a88646/ProtocolAbstraction",from_route_output="samples",to_route_input="samples",priority="2000000000",ms_telemetry="True"}
1040373
```

and this is an example message from the directory `/var/lib/aziot/storage/edgeHub/` which should have been deleted already because it’s expired → according to Copilot they are not delete if RefCount is still > 0
```
example message which should have been deleted already because it’s expired → according to Copilot they are not delete if RefCount is still > 0
```

## Additional Information
I think Copilot already found the root cause, see here my investigation:

and the problematic code is maybe because the messages are not deleted before RefCount becomes 0:
https://github.com/Azure/iotedge/blob/main/edge-hub/core/src/Microsoft.Azure.Devices.Edge.Hub.Core/storage/MessageStore.cs#L324