Timeout: use less resources, clean them up better and make cancellation deterministic

[Al2Klimov]

👍 Now we got unit tests!!! ❤️ 144abb1
👍 Now the destructor leads to cancellation. 21fc946
👍 Now the callback is "atomic", i.e. it doesn't yield. 32e64b6 175099c This way cancellation can't happen in a callback yield, making sure once cancelled, the callback won't (continue to) run. Also, we don't need any coroutine which has to carry around shared pointers which prevent own destruction...

closes #10250
closes #10252

[julianbrost]

Please add some documentation to the class. It now has some non-obvious details, especially regarding what happens at destruction (see #10254 (comment)).

The requested changes were addressed, so far I didn't get around to do a full review though.

[Al2Klimov]

@yhabteab Please could you have yet another look? After all

1. I've force-pushed this since Timeout: use less resources, clean them up better and make cancellation deterministic #10254 (review)
2. We need this if you don't want do exactly copy this PR in JsonRpcConnection: Don't drop client from cache prematurely #10210 (review)

[yhabteab]

Please resolve the conflicts! And please drop the Co-Authored-By: entry from bfb0303, that's just so unnecessary!

[yhabteab]

Drop incoming packets on one of the masters port. $ (sudo pfctl -sr 2>/dev/null; echo "block drop in on lo0 proto tcp from any to any port = 5666") | sudo pfctl -e -f - 2>/dev/null

[2025-01-08 10:27:40 +0100] critical/ApiListener: Cannot connect to host 'localhost' on port '5666': Operation canceled [system:89 at /opt/homebrew/include/boost/asio/detail/reactive_socket_connect_op.hpp:97:37 in function 'do_complete']
[2025-01-08 10:27:45 +0100] information/ApiListener: Reconnecting to endpoint 'satellite' via host 'localhost' and port '5666'
...
[2025-01-08 10:28:00 +0100] critical/ApiListener: Timeout while reconnecting to endpoint 'satellite' via host 'localhost' and port '5666', cancelling attempt
[2025-01-08 10:28:00 +0100] critical/ApiListener: Cannot connect to host 'localhost' on port '5666': Operation canceled [system:89 at /opt/homebrew/include/boost/asio/detail/reactive_socket_connect_op.hpp:97:37 in function 'do_complete']
[2025-01-08 10:28:05 +0100] information/ApiListener: Reconnecting to endpoint 'satellite' via host 'localhost' and port '5666'
...
[2025-01-08 10:28:20 +0100] critical/ApiListener: Timeout while reconnecting to endpoint 'satellite' via host 'localhost' and port '5666', cancelling attempt

[2025-01-08 10:43:11 +0100] warning/ApiListener: Timeout while processing incoming connection from [::1]:59149

Reactivate the standard firewall rules again: $ sudo pfctl -f /etc/pf.conf