Add services/container features from upstream Symfony Mailer component

There is code for above but for some reason I cannot create a MR from it.

Thanks.

1. The part about auto-wiring we definitely want and it should be applied to all services. There is an existing issue 📌 Consider marking some classes/functions @internal and find more convenient ways of dependency injection Active , and I put a link there to your code.
2. Everything relating to transports is going into core in 📌 [PP-1] Add symfony mailer transports to DIC Postponed . If that misses D10.2 then we would need to copy it into the Mailer Transport module (not here).
3. The Connections and StateTransport classes are more related to ✨ Add Symfony Messenger support for async messsages (emails as queues) Active which I don't think we need in this module, but it we do let's handle in the other issue.

>> The desire is to break out services into a dedicated issue.
When I said that I meant the first item above, and I meant to use the existing issue - sorry if that wasn't clear. Probably we don't really need this issue.

Alright, I assume you're carrying the code forward?

The scope is both not entirely clear to me and likely more effort than I wish to take on. Though I'm happy to coordinate on Messenger (and Mailer-service) related enhancements.