class Debugdata

The sink name and VMO are as described in the FIDL protocol's comments:

https://fuchsia.dev/reference/fidl/fuchsia.debugdata?hl=en#publisher

Send the fuchsia.debugdata.Publisher/Publish message in a pipelined open

on the "/svc" name table entry's client side, consuming this object. The

returned eventpair acts as a token; its lifetime represents the continued

mutability of the data in the VMO. If the VMO is mapped in and will be

touched until this process exits, then the handle can just be leaked with

a release() call. Otherwise it should be closed as soon as the VMO is no

longer being modified and not before (more or less), enabling the receiver

of the data to begin consuming it as soon as they are ready.

Consume the object like Publish but stuff the pipelined open message meant

for the "/svc" name table entry into the client end of a new channel, and

return its server end and token. This defers the actual transfer until

later, when the name table is available. At that time, the server end can

be passed to Forward.

When the Deferred::svc_server_end from a DeferredPublish call is plumbed

to where the svc_client_end is available, this forwards it roughly as if

Publish had been called on the original object instead of DeferredPublish.

(The Deferred::vmo_token from the earlier call must be plumbed separately

or has already been intentionally leaked or closed.)