Remove Zeek's batching of Broker messages

[jsiwek]

Initial investigations to remove Zeek-side batching were done in these PRs:

• Remove zeek::Batch and simplify API broker#64
• Remove Zeek-side batching of Broker messages #644

But findings indicate those changes may want to wait and re-evaluate after migrating to CAF 0.18 which aims to decrease cost of sending many smaller messages and avoid performance drop currently seen with these changes.

[rsmmr]

Looks like we're running out of time here, so moving to 4.1.0.

[rsmmr]

I think this is something to revisit once we have the new network protocol code landed in Broker.

[timwoj]

@rsmmr @Neverlord Have enough of the changes landed in Broker now to revisit this?

[Neverlord]

I believe so. I believe I did some benchmarking for this (with and without batching), probably a good idea to revisit that now.

[timwoj]

I'll throw it in the 5.1 project. Hopefully we can get it closed out.

[rsmmr]

Note that this comes with a risk of a major performance degradation in case that it doesn't quite work yet under heavy load. I would suggest we either do more testing first with the testing group before we merge, or we postpone for now in the spirit of not making large Broker changes this cycle.

[timwoj]

Ah yah, forgot about that. Taking it back out of the 5.1 project. We'll revisit it in 5.2.