HTTPCLIENT-2180. Implement warm-up functionality for PoolingAsyncClientConnectionManager

[arturobernalg]

This PR introduces the warmUp method for PoolingAsyncClientConnectionManager and PoolingHttpClientConnectionManager, allowing pre-initialization of connections to a target host. This functionality ensures connections are ready for immediate use, addressing performance concerns in latency-sensitive applications.

[ok2c]

I am sorry @arturobernalg but this looks wrong. The proposed code does not really "warm up" the pool. It merely creates a bunch of pool entries with no connection in them. It really makes no sense.

The only reliable way of creating a properly established connection is by executing a cheap request such as OPTIONS along the given route. Please note one needs a fully initialized and a functional client for that as a route may involve multiple hops, proxy tunnels and TLS security. It cannot be done by the connection manager alone.

If you really intend to resolve HTTPCLIENT-2180 you should probably create a utility class that executes a bunch of OPTIONS requests along the given route, but I would rather close HTTPCLIENT-2180 as "wontfix"

[arturobernalg]

wontfix

@ok2c agree to close the ticket as wontfix