[Bug] When ack receipts are enabled, no response is sent to the client if the topic has been unloaded or is being transferred

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### Read release policy

- [X] I understand that unsupported versions don't get bug fixes. I will attempt to reproduce the issue on a supported version of Pulsar client and Pulsar broker.

### Version

any released version, master branch

### Minimal reproduce step

This was found when analysing the source code, so no reproducer yet.
A test application that consumes and acks messages while a topic is being frequently unloaded will reproduce this issue.

### What did you expect to see?

When ack receipt is enabled, the broker should respond with a failure when it discards an ack.

### What did you see instead?

When the consumer isn't found, it's silently discarded. There's debug logging, but no ack receipt response logic to respond with an error:
https://github.com/apache/pulsar/blob/6c300f515dbf245620b14a844d9ff6215426e992/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/ServerCnx.java#L1982-L1988
and
https://github.com/apache/pulsar/blob/6c300f515dbf245620b14a844d9ff6215426e992/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/ServerCnx.java#L1952-L1960

### Anything else?

_No response_

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Start in pulsar-broker/src/main/java/org/apache/pulsar/broker/service/ServerCnx.java at the referenced lines around 1952-1960 and 1982-1988. Trace the ack handling path for missing consumers and how ack receipts are enabled, then reproduce with a consumer acknowledging messages while its topic is frequently unloaded. Done means discarded acknowledgements produce a failure response when receipts are enabled.

Written by the indexing model from the issue text.