The `Sandbox.SetKey()` method is called through an OCI prestart hook
which then calls back the daemon through a UNIX socket. This method is
responsible for provisioning interfaces, etc... into the sandbox.
A new EnvironCarrier is used to propagate the trace context to the
prestart hook, which then marhsals an OTel MapCarrier into the JSON
payload sent back to the daemon. That way, every spans created from
`SetKey()` are correctly parented to the original `ContainerStart` API
call.
Signed-off-by: Albin Kerouanton <albinker@gmail.com>
