feat(konnect): add namespace in KonnectNamespacedRef

[randmonkey]

What this PR does / why we need it:
Add namespace in konnectNamespacedRef because some of Kong entities like KongVault and KongClusterPlugin are cluster scoped and they require the namespace for referring to a Konnect gateway controlplane.
Which issue this PR fixes

#36

Special notes for your reviewer:

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect significant changes

[pmalek]

For now we've decided to not implement cross namespace references.

Kong/gateway-operator#524 for example has been put into 'post-GA' part of the epic.

Let's first solve the immediate scope from Kong/gateway-operator#370 (for October's release).

LMKWYT

[randmonkey]

For now we've decided to not implement cross namespace references.

Kong/gateway-operator#524 for example has been put into 'post-GA' part of the epic.

Let's first solve the immediate scope from Kong/gateway-operator#370 (for October's release).

LMKWYT

KongVault is also cluster scoped. If we do not want to add namespace, it should also be moved out of KGO 1.4 scope.

[pmalek]

Left a comment about this in https://kongstrong.slack.com/archives/C079GK3KB9R/p1726654138359599.

IMHO we should prevent using cross-namespace refs until we implement proper handling of those. In order to move forward with Vaults, let's review and merge this but at the same time let's add CEL validation rules to other types that will prevent users from using cross namespace ref in non cluster scoped resources.