Resolve "nexus_writer: autof and manual saving how to solve link to images"

Closes #1899 (closed) #2890 (closed)

The autofilter patched acquisition objects have two lists of channels

• acq_obj.device.channels contains all OLD_CHAN
• acq_obj.channels contains all NEW_CHAN

This is what we are trying to achieve:

reading task --> OLD_CHAN.emit --new_data--> new_data_received --> NEW_CHAN.emit --new_data--> Publish in Redis

The Louie connections are made:

• OLD_CHAN.emit --new_data--> new_data_received: done on instantiation
• NEW_CHAN.emit --new_data--> Publish in Redis: done by the scan object in Scan._prepare_devices

The problem is that sometimes NEW_CHAN.emit gets called and sometimes OLD_CHAN.emit.

In this MR I try a different approach: patch the acquisition chain in-place (so we keep all original acquisition objects and channels). This mostly involves patching the emit method of all channels to block emitting invalid points.