feat(transparent-proxy): allow --kuma-dp-user to accept UIDs and deprecate --kuma-dp-uid flag

[bartsmykla]

Move Owner UID/Username Processing to Config

• Enhanced --kuma-dp-user Flag:
  • The --kuma-dp-user flag in kumactl install transparent-proxy now accepts both usernames and UIDs.
  • The --kuma-dp-uid flag has been deprecated in favor of the enhanced --kuma-dp-user flag.
  • The --kuma-dp-user flag is now optional. If not specified, the system will attempt to use a default UID (5678) or the default username (kuma-dp).
  • The logic for processing user information (searching for the user) has been moved to the transparent proxy Config.

Small Improvements and Refactorings

• Add IPFamilyMode to Config and Remove IPv6 Field:

  • Replaced the IPv6 field in Config with the IPFamilyMode field.
  • This change centralizes the processing of IP family modes within the Config struct, simplifying the configuration and usage.

• Unembed Executables from InitializedExecutables:

  • Removed the embedding of the Executables struct from InitializedExecutables.
  • The fields from Executables are not used directly in InitializedExecutables, and unembedding helps to reduce clutter and improve code clarity.

• Adjust Unit Tests for kumactl install transparent-proxy:

  • Updated the unit tests to align with recent changes in handling IPv4 and IPv6 rules generation.
  • Removed the use of subnetPlaceholder and unified the IP address for inbound traffic in tests, as there is no different inbound redirection port for IPv6 now.

Checklist prior to review

• Link to relevant issue as well as docs and UI issues
  • Add a more systematic way to add transparent-proxy config #8324
• 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)
  • Existing unit tests adjusted
  • Manually tested on local Ubuntu:24.04 container
  • Don't forget ci/ labels to run additional/fewer tests
• Do you need to update UPGRADE.md?
  • Updated
• 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)
  • There is no need