Retire the old "raw" event format

[nblumhardt]

Since Seq 3.3, three and a half years ago, Seq has supported and been encouraging the use of the Serilog.Formatting.Compact "compact log event format" (CLEF) for ingestion.

It has the benefits of requiring less network bandwidth and storage space, being quicker to parse, and being supported by a variety of tools (e.g. seqcli, clef-tool, Serilog.Formatting.Compact.Reader, and https://github.com/warrenbuckley/Compact-Log-Format-Viewer).

While the sink has offered compact format as an option for some time, the older "raw" format was kept as the default for compatibility reasons. We could change the default and provide raw format as an option, but with the dwindling number of Seq 3.2 and earlier servers still in service, I think it's reasonable to pull out "raw" support altogether, and improve the overall maintainability of this codebase.

This PR removes compact:, and all of the underlying support for it, except for where it's necessary to ingest already-written durable file sets.

[KodrAus]

More deletions than additions? Looks good to me!

[xantari]

Which log format does the Seq Forwarder use (both the legacy forwarder, and the new .net core version of the tool)? Wondering how that plays into this log format question as we are diagnosing an issue where the logs aren't arriving to our Seq server and we are using a very ancient version of the Seq forwarder and wondering if that is perhaps the cause.

[nblumhardt]

Hi @xantari! The 2.0+ versions of the forwarder support both formats; the older 1.x versions only support the original "raw" format (and so will need older versions of this sink, to keep working). HTH!