Panic in pattern ingester read path

[cyriltovena]

Seems like we can sometimes panic with errors like runtime error: makeslice: cap out of range looking at the stacktraces it seems to come from https://github.com/grafana/loki/pull/12703/files#diff-472ead11f0a321ec18f4d3cb58f65a59bc7e8b3a172fc00e77a8dc10830d676cR75

[benclive]

Opened a fix in #13010. The root cause seems to be out-of-order writes to the pattern ingester which are rare but perfectly valid, so we just need to handle them.