feat(kuma-cp): allow using Dataplane kind in top level targetRef in all policies

[Automaat]

Motivation

As in pr title, we want to use top level targetRef kind Dataplane in all policies

[github-actions]

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[lobkovilya]

wait, but the stuff in ResourceDescriptor is static and depends on the policy type, right? we should allow/disallow sectionName based on the actual presence of from or rules. For example, if MeshTimeout has only to and ResourceDescriptor.HasFromTargetRef is true we still shouldn't allow sectionName

[Automaat]

@lobkovilya I've circled back to isInboundPolicy option

[lobkovilya]

probably you need to add some unit tests in validation, as there were no failures with incorrect approach

[Automaat]

@lobkovilya I've added this test previosly:

kuma/pkg/core/resources/apis/mesh/validators_test.go

Lines 1030 to 1040 in 1bbc414

	opts: &ValidateTargetRefOpts{
	SupportedKinds: []common_api.TargetRefKind{
	common_api.Dataplane,
	},
	},
	expected: `
	violations:
	- field: targetRef.sectionName
	message: can only be used with inbound policies
	`,
	}),

[lobkovilya]

No I mean initially you've passed IsInboundPolicy: true to the validator without checking len(r.Spec.From) > 0). We agreed that it was incorrect, and I think that some tests should've failed. But since no tests failed I assume we're missing some tests, right?