Port promtail fix to docker logs split into multiple frames

[LegoFed3]

What's wrong?

Earlier this year a bug in promtail was fixed (see grafana/loki#12374) that prevented unwanted timestamps from being inserted into long log lines. The same problem is still present in alloy as of v1.4.2 - could the fix be ported in here as well?

Steps to reproduce

See grafana/loki#12197

System information

Linux 6.1.0-25-amd64

Software version

Grafana Alloy v1.4.2 (docker image, the problem existed also on v1.2.1)

Configuration

No response

Logs

No response

[matteo-zanoni]

+1 also experiencing this! A fix would be great

[github-actions]

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