feat(core): add getResultAndCount()

[erie0210]

Closes #3885

[B4nan]

Suggested change

	## Paginate queries
	## Pagination

[B4nan]

this belongs to the paragraph above

[B4nan]

Suggested change

	If we want to paginate results, we can use `qb.getResultAndCount` method. It returns both array of results and total count query without offset and limit
	If we want to paginate the results of a QueryBuilder, we can use `qb.getResultAndCount()` method. It returns an ordered tuple, the first item being an array of results, and the second one being the total count of items, discarding the limit and offset clause.

[B4nan]

Suggested change

	const qb = orm.em.createQueryBuilder(FooBar);
	qb.select('*')
	.where({ name: 'fb 1' })
	.limit(10);
	const [results, count] = qp.getResultAndCount();
	console.log(authors.length); // based on limit parameter, e.g. 10
	console.log(count); // total count, e.g. 1327
	const qb = em.createQueryBuilder(User);
	.select('*')
	.where({ age: 18 })
	.limit(10);
	const [results, count] = await qb.getResultAndCount();
	console.log(results.length); // max 10, as we used the limit clause
	console.log(count); // total count regardless limit and offset, e.g. 1327

[B4nan]

Suggested change

	const [results, count] = await Promise.all ([
	this.getResultList(),
	this.getCount(),
	]);
	return [results, count];
	return Promise.all([
	this.getResultList(),
	this.getCount(),
	]);

[erie0210]

PR fixed! Thanks for the review. 👾 @B4nan

[B4nan]

looking good, thanks!