Aspnetcore: Consider tracing span id and trace id separately in the log

[davidfowl]

Seems to like open census:

https://github.com/census-instrumentation/opencensus-specs/blob/c3fd41b28fed96ceffc8c35af280d74cacea3ab2/trace/LogCorrelation.md#key-names-for-tracing-data

cc: @SergeyKanzhelev @lmolkova

[lmolkova]

We should use W3C trace context notions (OpenCensus names are the same) probably in CamelCase as other scopes.

To make it useful we need to log parent-id as well otherwise we lose causation in the logs. When an incoming request is received, it gets TraceId and ParentId in the headers. New SpanId is generated.
So I propose to log all three.

Also, assuming we keep Activity default behavior (which is Request-Id if there is no incoming w3c header), we have to map legacy format to these names.

• TraceId is Activity.RootId
• ParentId is Activity.ParentId
• SpanId is Activity.Id // This seems to be very confusing.

[davidfowl]

Verifying this is blocked on #11404

[davidfowl]

[davidfowl]

Verified in 3.0.0-preview7.19326.6