chore(kuma-cp): create a list of outbounds to use in plugins instead of the dpp.networking.outbound

[lobkovilya]

Today mesh_proxy_builder.go and dataplane_proxy_builder.go always set a list of outbounds to the dataplane.spec.networking.outbound field. The field is a proto field (so it's a public API), it limits us in adding additional info to outbounds.

This PR creates a new list Outbounds in the Proxy structure, all new plugins should take outbounds from this list. In the next PR, the Outbound structure will get additional field ResourceIdentifier for new outbounds.

Checklist prior to review

• Link to relevant issue as well as docs and UI issues --
• This will not break child repos: it doesn't hardcode values (.e.g "kumahq" as a image registry) and it will work on Windows, system specific functions like syscall.Mkfifo have equivalent implementation on the other OS --
• Tests (Unit test, E2E tests, manual test on universal and k8s) --
  • Don't forget ci/ labels to run additional/fewer tests
• Do you need to update UPGRADE.md? --
• Does it need to be backported according to the backporting policy? (this GH action will add "backport" label based on these file globs, if you want to prevent it from adding the "backport" label use no-backport-autolabel label) --