Avoid boxing of TState about serilog-extensions-logging

[jods4]

Nothing is ever trivial 🤣
Turns out StartsWith(char) was not part of .net fx of good ole time, so I reverted.

Could have gone creative with str is ['@', ..], turns out that as optimal as it gets. Felt excessive, though 😏

[jods4]

Another cheap win in .net < 9.0: StartsWith(char) is quite faster than StartsWith(string) on these two lines:
https://github.com/serilog/serilog-extensions-logging/blob/dev/src/Serilog.Extensions.Logging/Extensions/Logging/SerilogLogger.cs#L106-L111

In .net 9+ there's a fast path in StartsWith(string) that checks if (prefix.Length == 1) return str.StartsWith(prefix[0]).

[jods4]

BTW: it would be nice to have similar fast logging when using Serilog natively!

• MS code generator only targets M.E.L.ILogger, we'd need a generator whose template targets Serilog.ILogger.
  Source code is here: https://github.com/tkrafael/dotnet-runtime/tree/693620ed1425182d1f388f51f06fa18fb6b7e142/src/libraries/Microsoft.Extensions.Logging.Abstractions/gen
  It would also be nice to fallback to global static Log on static methods if there's no static ILogger in class.

• Code that writes a struct + formatter efficiently would need to be moved from Serilog.Extensions.Logging into Serilog core.

[nblumhardt]

Thanks for all the thoughts and suggestions @jods4!

Anyone keen to investigate/PR any of these? 😎

[jods4]

@nblumhardt The first changes are so trivial... here you go: #242

I should have opened a different issue for having performant code generator that works with Serilog.Log.
That's a whole lot more complicated, cannot be closed as quickly 😆

[nblumhardt]

Thanks again, keen to keep chipping away at these kinds of things, nice to see small gains add up over time :-)