Fix schema authz check for non-CCloud message viewer instances

[shouples]

#654 started using LocalEnvironments and introduced DirectEnvironments, but there is still an old leftover assumption that local Kafka topics don't have an associated environmentId (which is false, since they have the vscode-local-connection ID):

vscode/src/authz/schemaRegistry.ts

Lines 29 to 48 in aca3bf5

	export async function canAccessSchemaTypeForTopic(
	topic: KafkaTopic,
	type: "key" | "value",
	): Promise<boolean> {
	if (!topic.environmentId) {
	// no way of checking local topic schemas currently
	return true;
	}
	const environmentId: string = topic.environmentId;
	const schemaRegistry: CCloudSchemaRegistry | null =
	await getResourceManager().getCCloudSchemaRegistry(environmentId);
	if (!schemaRegistry) {
	logger.debug(
	"no Schema Registry in extension state matching CCloud topic's environment ID; assuming user can access (non-existent) schemas",
	{ environmentId },
	);
	// if we had schemas, we would have a schema registry
	return true;
	}

So when opening message viewer for a local/direct Kafka topic, we see these in the logs:

no Schema Registry in extension state matching CCloud topic's environment ID; assuming user can access (non-existent) schemas { environmentId: "vscode-local-connection" / <UUID> }

We need to update this to correctly handle local/direct environments and migrate it to using the appropriate ResourceLoader instances.