fix(policy): improve targetRef name and tags validation

[alparslanavci]

Added validation for targetRef name and tags as required. Also, MeshGateway and MeshHTTPRoute kind validations are included.

Fix #7912

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) --
• 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) --
• Do you need to explicitly set a > Changelog: entry here or add a ci/ label to run fewer/more tests?

[slonka]

@bartsmykla @Automaat can you take a look at this? also @lobkovilya might be interested

[bartsmykla]

few nits but lgtm overall

[alparslanavci]

Thanks for the review, @bartsmykla!

[lahabana]

I think we're reintroducing things that already exists.

[bartsmykla]

@alparslanavci I allowed myself to address @lahabana remarks. Please have a look if everything is ok for you and I would merge it then.

[alparslanavci]

Thanks for the help, @bartsmykla! I was a bit busy in the last few days, couldn't find a chance to address the comments. I am ok to go ahead 👍

(I think we tried to fix the failing tests at the same time, thus I reverted my latest commit.)