LoggerMessage interceptor for LoggerExtension methods

[alrz]

LoggerMessageAttribute was introduced to make it easier to use LoggerMessage.Define, however it still needs a partial declaration for each log line to migrate.

Using roslyn interceptors, each callsite can be replaced with a helper that calls into a LoggerMessage delegate, generated specifically for each usage.

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[alrz]

I think as part of this, LogPropertiesAttribute could be integrated so that using some syntax like @-prefix, the logger logs properties the same way LogPropertiesAttribute does. I think that would require some of the functionality to be pulled to runtime, or perhaps host this generator in dotnet/extensions?