Client-side savedObject client: optimize `bulk` get pooling

[pgayvallet]

The client-side savedObject client is using a pooling mechanism for get operations

kibana/src/core/public/saved_objects/saved_objects_client.ts

Lines 362 to 371 in d4b2a51

	public get = <T = unknown>(type: string, id: string): Promise<SimpleSavedObject<T>> => {
	if (!type || !id) {
	return Promise.reject(new Error('requires type and id'));
	}
	return new Promise((resolve, reject) => {
	this.batchQueue.push({ type, id, resolve, reject } as BatchQueueEntry);
	this.processBatchQueue();
	});
	};

kibana/src/core/public/saved_objects/saved_objects_client.ts

Lines 162 to 167 in d4b2a51

	private processBatchQueue = throttle(
	() => {
	const queue = cloneDeep(this.batchQueue);
	this.batchQueue = [];
	this.bulkGet(queue)

When calling client.get multiple times with the same type/id tuple, the resulting bulkGet that fires contains these duplicates.

We should remove the dupes when calling the backend, and then optimize the logic to dispatch (copies of) the object to the get calls that requested the same object.

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)