fix kafka decoding error blocking consumption

[matthieugouel]

For some reason we received a non utf-8 message from Kafka topic, and the application is getting stuck with this error:

Process Process-27:
Traceback (most recent call last):
  File "/usr/lib/python3.11/multiprocessing/process.py", line 314, in _bootstrap
    self.run()
  File "/usr/lib/python3.11/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3/dist-packages/napalm_logs/listener_proc.py", line 102, in start
    log_message, log_source = self.listener.receive()
                              ^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/napalm_logs/listener/kafka.py", line 83, in receive
    log_source = log_source.decode()
                 ^^^^^^^^^^^^^^^^^^^
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xa2 in position 1: invalid start byte

This fix try catch on the initial key decoding and return and follow the same error handling pattern as the message json decoding below.

[mirceaulinic]

Odd. The tests aren't passing, but many things are broken here, this repo needs some love and I'll make some time soon for a refresh & release. Thanks for your contribution @matthieugouel!