http resolve to support scheme and port change

[guoweis-work]

Currently, the resolver can handle something like this

- type: http
  resolve:
    - siteA:8080:siteB

This changes from http://siteA:8080 to http://siteB:8080

In my use case, I need to change the port as well.

- type: http
  resolve:
    - https:siteA:443:http:siteB:8080

This changes from https://siteA:443 to http://siteB:8080

If I submit a PR for this, would you be open to take this? This will be an alternative, additional syntax of resolve.

If the scheme is too out of scope, what if just the port?

- type: http
  resolve:
    - siteA:7070:siteB:8080

This changes from http://siteA:7070 to http://siteB:8080

[fsamin]

Hello,
This could be an interesting feature in the http executor. If you want to submit a PR, it would be appreciated.