feat(meshexternalservice): allow traffic when using egress, remove MTP support

[lukidzi]

Checklist prior to review

In a previous release, we added MeshExternalService (MES) support for dataplanes and egress. We decided that the top targetRef would select dataplanes, and for the purposes of MES and egress, we introduced this in that release. Since it's an experimental feature, we can safely remove it.

• Remove MeshExternalService from topTargetRef (since it's experimental, we don't need to deprecate it: see MeshExternalService).
• Add a default allow-all RBAC configuration on egress for MES, with an option to disable it for all MES.

Merge after #11073

• Link to relevant issue as well as docs and UI issues -- xrel https://github.com/Kong/kong-mesh/issues/6180
• 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) --