async-callback should not be invoked for filtered out items

[plastikfan]

The async wrapper is not decorating in the correct position, so it sees items that will be filtered out. This is inefficient and should be avoided.

[plastikfan]

Actually, there is little value in fixing this because one of the points of creating the lorax project with its intended reactive model, is to simplify the initialisation sequence of extendio's navigator. The proper fix to this is the reactive model which will make this all much easier. For now, there is the problem of the filtering only applying after the async, which is too late and there isn't a quick workaround. I did think that inserting the async callback before the filter is initialised, but that would not work as it would require storing the context inside a struct, which I'm trying to avoid at all costs (I would rather build the entire required reactive model than take that route).

As a reminder to oneself, the intention is to create a sequence something like:

gorx.New(options).Filter(filter options).WithPool().Consume(...).Run(ctx, cancel)

or

gorx.New(options).Listen(listen options).Filter(filter options).Run()

or

gorx.Resume(resume options).WithPool(...).Run(ctx, cancel)

or

gorx.Resume(resume options).Run()

For the purposes of resume, all options would have to be collected and restored.

In the above, the options specified in new, do not include information relating to filters or listen as they are passed into those operators directly.

One thing that was discovered was that LabelledTraverseCallback was being referenced by value rather than be pointer, so this has been fixed.

[plastikfan]

ensync BEFORE:

raw: filter
client: listener
decorated: listener
decator: boost

AFTER:
raw: filter
client: boost
decorated: listener -> N/A
decorator: boost

PROXY:

frame.raw: filter
frame.client: boost -> listener

INSIDE BOOST:
decorated.Fn: listener ==> ie the thing its delegating to is not the filtered item

this is being caused by the bad decision to use the raw pointer; this is confusing everything and making the code brittle and hard to work with

WORKER: