Warn rather than fail if the webcam is not found

[DominicOram]

Occasionally the webcam can become offline (see https://ispyb.diamond.ac.uk/samples/sid/5853099). Given that the webcam is only really for troubleshooting issues Hyperion should be happy without it so if it is offline we should just log a warning and continue.

Acceptance Criteria

• Hyperion will log a warning and continue if the webcam is offline

[DominicOram]

I have a hotfix on the beamline that does this but it requires more investigation as to why we are failing at all. GDA reads from the same webpage and does not regularly fail to get an image. The only differences between how GDA does it and how we do it are:

• We use aiohttp, GDA uses urllib
• We explicitly raise on error codes, GDA does not and will always try and read the data

The hotfix on the beamline now does not check for error codes and carries on anyway, we should keep an eye on it and see if there are cases where we get an error code but still get a valid image. In which case we should just ignore the error code (maybe logging a warning)