Add native tracing fields to LogEvent to eliminate async MDC overhead

[ramanathan1504]

Fixes #1976 by introducing a TraceContextProvider SPI and adding
native W3C tracing fields (traceId, spanId, traceFlags) directly to LogEvent.

This allows frameworks like OpenTelemetry to bypass the ThreadContext map
entirely, eliminating the map-cloning memory overhead previously
required during asynchronous logging.

[rgoers]

I see no reason not to do this. The implemenation looks pretty simple and clean. However, I don't see an integration with JsonTemplateLayout. Is one needed? Without that how would the data get injected into ElasticSearch?

[ramanathan1504]

Hi @rgoers, that is a great point. I hadn't included the JsonTemplateLayout integration yet, but it is definitely needed to support structured logging properly.

Should I push the native JTL resolvers as new commits to this PR, or would you prefer I open a separate PR since this one is already approved?