trace: implement provider payload

trace: implement provider payload

The trace function payloads such as rte_trace_point_emit_* have
dual functions. The first to emit the payload for the registration
function and the second one to act as trace mem emitters a.k.a
provider payload.

When it is used as provider payload, those function copy the trace
field to trace memory based on the tracing mode.

Added payload definitions under ALLOW_EXPERIMENTAL_API define
to allow the existing applications to compile without enabling
experimental APIs.

Signed-off-by: Jerin Jacob <jerinj@marvell.com>
Signed-off-by: Sunil Kumar Kori <skori@marvell.com>
Acked-by: David Marchand <david.marchand@redhat.com>