routing problem for domains with different IP behaviors

[patterniha]

the #4335 issue has become very messy and confusing and many people have misunderstood the problem.
although it was my fault that I couldn't express the problem correctly.

Problem:

assume that built-in-dns return [ip1, ip2] in answer of dns-query for the domain "example.com".
and we want to use ip2 in outbound.

but with the current capabilities of Xray-core this is not possible, even with using features like: loopback, dialerProxy, IPOnDemand, sniffing,...

Application1:

assume that twimg.com return [ip1, ip2]
and ip1 is behind cloudflare and ip2 is behind fastly.
and we have two outbounds: the first is cloudflare-worker(that doesn't support cloudflare ips) and the second is freedom-fragment.

and we want to use worker as much as possible.
so we should choose ip2 and worker-outbound.

Application2:

we have two outbounds: the first is tls-repack-domain-fronting and the second is freedom-fragment: example

cloudflare-ips doesn't support domain-fronting.
but we want to use domain-fronting as much as possible.
so we should choose ip2 and tls-repack outbound.

Suggested solutions:

1. this
2. in routing rules we save all matched-things in ctx and then use in outbound