Jaeger Grpc Exporter export Span Data with trace flags

[blueswhisper]

Is your feature request related to a problem? Please describe.
Jaeger Collector Proto has define flags field. But SpanMarshaler not write trace flags when postSpan request.

[jkwatson]

Before implementing this, I'd like to have this added to the opentelemetry specification for the Jaeger exporter.

[blueswhisper]

Any schedule for this specification I can track ?

[jkwatson]

Any schedule for this specification I can track ?

someone (you?) will need to drive this to happen. It won't happen without a sponsor and someone willing to make sure it happens. :)

[jack-berg]

The jaeger exporters were removed in #6119 so this is no longer relevant.