mqtt-replay: Add CLI option to override publish topic

[scfct]

As developers, we occasionally encounter scenarios where recorded messages under one topic hierarchy (e.g. v2x/loopback/#) need to be replayed on a different topic path (e.g. v2x/rx/#). To simplify this workflow, it’s helpful to provide a built-in way to redirect topics during playback.

This PR introduces a new CLI option for the mqtt-replay utility that allows overriding the recorded topic, enabling more flexible testing and integration with different topic structures.

[BendixBuchheister]

I am not sure how much this helps, when all messages are published on the same topic tho.
Normally we record topics with wildcard subscriptions

[jbeyerstedt]

Have you looked into the bridging functionality of mosquitto? Because that can forward messages from one topic to another even with rewriting a topic prefix.

I think, that rewriting the recorded topic(s) can be useful feature. But replacing all recorded topics with a single one serves a very limited scope and may even be a bit dangerous. Therefore I see two possible things that can be a future feature of this application:

• either combine it with a filter which specifies which topic (wildcard) from the recording is re-published during playback. Then you could single out a recorded topic and replace that with another one.
• or extend the CLI option to support the MQTT bridge-topic syntax like pattern record-prefix publish-prefix to add, remove or rewrite prefixes.