chore: introduce index for DataPlanes referencing KongPluginInstallations

[programmer04]

What this PR does / why we need it:

Implements what was mentioned in the comment #476 (comment) during the review - index for DataPlanes that references KongPluginInstallations to avoid fetching all of them and filtering in the code.

Which issue this PR fixes

Improvement for #380

Special notes for your reviewer:

The code for indices for Konnect entities and other ones may one day be merged, but this is out of the scope of this PR. Only to make it similar in terms of what is logged has been addressed. Furthermore, log format seems a little redundant

KongPluginBinding	creating index	{"entityTypeName": "KongPluginBinding", "indexObject": {"metadata":{"creationTimestamp":null},"spec":{"pluginRef":{"name":""},"targets":{}},"status":{}}, "indexField": "kongPluginRef"}
KongPluginBinding	creating index	{"entityTypeName": "KongPluginBinding", "indexObject": {"metadata":{"creationTimestamp":null},"spec":{"pluginRef":{"name":""},"targets":{}},"status":{}}, "indexField": "kongServiceRef"}
KongPluginBinding	creating index	{"entityTypeName": "KongPluginBinding", "indexObject": {"metadata":{"creationTimestamp":null},"spec":{"pluginRef":{"name":""},"targets":{}},"status":{}}, "indexField": "kongRouteRef"}
KongPluginBinding	creating index	{"entityTypeName": "KongPluginBinding", "indexObject": {"metadata":{"creationTimestamp":null},"spec":{"pluginRef":{"name":""},"targets":{}},"status":{}}, "indexField": "kongConsumerRef"}

Now it's like that

2024-09-27T17:46:22+02:00	INFO	ControlPlane	creating index	{"indexField": "dataplane"}
2024-09-27T17:46:22+02:00	INFO	DataPlane	creating index	{"indexField": "KongPluginInstallations"}
2024-09-27T17:46:22+02:00	INFO	KongPluginBinding	creating index	{"indexField": "kongPluginRef"}
2024-09-27T17:46:22+02:00	INFO	KongPluginBinding	creating index	{"indexField": "kongServiceRef"}
2024-09-27T17:46:22+02:00	INFO	KongPluginBinding	creating index	{"indexField": "kongRouteRef"}
2024-09-27T17:46:22+02:00	INFO	KongPluginBinding	creating index	{"indexField": "kongConsumerRef"}
2024-09-27T17:46:22+02:00	INFO	KongPluginBinding	creating index	{"indexField": "kongConsumerGroupRef"}

[pmalek]

Some nits but overall this looks good.