BRNGG-36274-Add integration tests for parse error handling

[ormelaver-cyber]

Important Note

After further discussion, it was decided that we REMOVE the throw error when we get a SyntaxError. This was a bug that we initially decided to leave as is.
Apparently amqplib, which is the one that eventually calls consumeFunc (via channel.consume(queue, consumeFunc, { noAck: false })), does not await so there is no option to catch the error that we throw.
Now if clients want to handle the error, they must register to the afterProcessMessage callback that is invoked in _rejectMessageAfterProcess

Add integration tests for consumer parse error handling

• Test callback is not invoked when JSON parsing fails
• Test afterProcessMessage hook receives SyntaxError
• Test messages are rejected without requeue (verified via messageCount)
• Test valid messages continue processing after parse errors
• Test empty string with JSON content type as edge case
• Test RPC returns SyntaxError to producer on invalid request