Remove IsPureDirectResource hack

[jasonvigil]

Checklist

• I did not find a related open enhancement request.
• I understand that enhancement requests filed in the GitHub repository are by default low priority.
• If this request is time-sensitive, I have submitted a corresponding issue with GCP support.

Describe the feature or resource

Similar to #3443, we have an opportunity to remove the need for the IsPureDirectResource hack. It's probably possible to compute these values, instead of hardcoding them.

k8s-config-connector/pkg/test/resourcefixture/sets.go

Lines 89 to 111 in cd511f7

	func IsPureDirectResource(gk schema.GroupKind) bool {
	pureDirectResources := []string{
	"ApigeeEnvgroup",
	"BigQueryConnectionConnection",
	"BigQueryDataTransferConfig",
	"CloudBuildWorkerPool",
	"DataformRepository",
	"FirestoreDatabase",
	"NetworkConnectivityServiceConnectionPolicy",
	"PrivilegedAccessManagerEntitlement",
	"RedisCluster",
	"BigQueryAnalyticsHubDataExchange",
	"BigQueryAnalyticsHubListing",
	"WorkstationCluster",
	"WorkstationConfig",
	"Workstation",
	"KMSAutokeyConfig",
	"KMSKeyHandle",
	"SecureSourceManagerInstance",
	"SecureSourceManagerRepository",
	}
	return slices.Contains(pureDirectResources, gk.Kind)
	}

We should also update the direct controller guide to remove instructions related to this manual update:

k8s-config-connector/docs/develop-resources/deep-dives/5-releases.md

Line 30 in cd511f7

* For resource that is purely direct controller based, add the resource name to `pureDirectResources` in `IsPureDirectResource` function in [sets.go](https://github.com/GoogleCloudPlatform/k8s-config-connector/blob/master/pkg/test/resourcefixture/sets.go).

Additional information

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Importance

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