Serilog.Sinks.OpenTelemetry.Formatting.CleanMessageTemplateFormatter
Matches the `:lj` clean formatting style now employed by Serilog.Expressions, Serilog.Sinks.Console, and elsewhere.
In this mode, strings embedded in message templates are unquoted, and structured data is rendered as JSON.
public static string Format(MessageTemplate messageTemplate, IReadOnlyDictionary<string, LogEventPropertyValue> properties, IFormatProvider formatProvider)