feat: add local/remote sub cache to publisher

[wyfo]

Current Publisher::put workflow always try to check if there are both local and remote subscribers, and these operations are costly, e.g. more than 10% of the time spent in checking local subscribers. However, the information is known, at least can easily be retrieved, and it could be used to save a lot of CPU consumption in case of remote-only/local-only workflow.

The PR does it by adding a cache to the publisher, to store if there are no remote and/or no local subscribers, in order to shortcut the put workflow. The cache is an atomic integer, directly stored in the publisher, with one bit flag for each information. Both remote and local routing functions has been updated to return a boolean saying if there was a matching route/subscriber, in order to update the cache.
Also, in order to reset the cache when there are new remote/local subscribers detected, the session keep a subscription_version integer field, incremented each time there is a new subscriber (at the same place where matching listener are notified). The version is also stored in the remaining bits of the cache, and if both don't match, the cache is reset with the current version. To not care about version rollover, a 64bit integer is used, which let 62bit used for the version (because of two bit flags) in the cache, so more than enough.

[github-actions]

PR missing one of the required labels: {'dependencies', 'enhancement', 'documentation', 'bug', 'breaking-change', 'new feature', 'internal'}

[yellowhatter]

Let's refactor cache to be an object with methods like set_no_remotes() etc to make code cleaner and more readable.

[wyfo]

The issue is that resolve_put is shared with Session::put workflow, in which there is no cache. Because I'm not sure that resolve_put is inlined, I've written the code in the "most efficient" way using a dummy cached value . But using a PublisherCache type when there is no publisher is quite odd...

[wyfo]

I will try to restructure the code

[yellowhatter]

Need some brush-up

[wyfo]

I've extracted the caching logic into dedicated types. The result is slightly less performant by 1-2% than the previous version — even after adding an other optimization preventing the payload clone if there is no local sub — but I don't think we care, as it's still a lot more performant than the current main branch by more than 15%

[OlivierHecart]

The z_local_pub_sub_thr example needs to be removed.

The cache disabling in WeakSession::send_declare is not enough. For example after connecting to a new router/peer data is routed to this peer until the Declare<Sub> or Declare<Final> is received. So cache should be invalidated on new transport and re invalidated on Declare<Sub> or Declare<Final>.
All points where cache invalidation should occur need to be identified. And a notification needs to be established to the Session.