fix(kuma-dp): fix incorrect dataplane name due to mangled env vars

[bartsmykla]

Kubernetes workloads may have their environment variables mangled by other components outside of our control. This can cause the POD_NAME or POD_NAMESPACE variables to be defined after the KUMA_DATAPLANE_NAME variable, which results in an incorrect dataplane name.

This commit fixes this issue by checking for the POD_NAME and POD_NAMESPACE variables directly during Kuma dataplane runtime initialization if KUMA_DATAPLANE_NAME is empty or contains the characters $(){}, which suggests that the dependent variables were not present before its definition. This involved adding a PostProcess method to the Config interface.

Checklist prior to review

• Link to relevant issue as well as docs and UI issues
  • there is no relevant issue
• 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
  • it won't
• Tests (Unit test, E2E tests, manual test on universal and k8s)
  • unit tests were added
  • manually tested on local k3d cluster
  • Don't forget ci/ labels to run additional/fewer tests
• Do you need to update UPGRADE.md?
  • there is no need
• 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)
  • it does

[lahabana]

missing zoneProxy helm chart configuration change.

[lahabana]

Approved! THough I'm not sure we should backport this as it changes quite a lot.