fix(loki.source.syslog): UDP path returns EOF

[github-vincent-miszczak]

PR Description

When using loki.source.syslog with udp, all messages are broken for Grafana Agent with error message

msg="error parsing syslog stream" component=loki.source.syslog.syslog err="unexpected EOF"

ex: logger -d -n localhost -P 1514 'test: test' => you get the error.
Same with Docker as Syslog message producer.

The issue comes from using TCP stream framing for UDP, which is incorrect.

Notes to the Reviewer

PR Checklist

• CHANGELOG.md updated
• Documentation added
• Tests updated
• Config converters updated

[CLAassistant]

All committers have signed the CLA.

[github-actions]

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[github-actions]

This PR has not had any activity in the past 30 days, so the needs-attention label has been added to it.
If you do not have enough time to follow up on this PR or you think it's no longer relevant, consider closing it.
The needs-attention label signals to maintainers that something has fallen through the cracks. No action is needed by you; your PR will be kept open and you do not have to respond to this comment. The label will be removed the next time this job runs if there is new activity.
Thank you for your contributions!