feat(core): add Collection.matching() method to allow pagination

[B4nan]

Collections now have a matching method that allows to slice parts of data from a collection.
By default, it will return the list of entities based on the query. We can use the store
boolean parameter to save this list into the collection items - this will mark the
collection as readonly, methods like add or remove will throw.

const a = await em.findOneOrFail(Author, 1);

// only loading the list of items
const books = await a.books.matching({ limit: 3, offset: 10, orderBy: { title: 'asc' } });
console.log(books); // [Book, Book, Book]
console.log(a.books.isInitialized()); // false

// storing the items in collection
const tags = await books[0].tags.matching({
  limit: 3,
  offset: 5,
  orderBy: { name: 'asc' },
  store: true,
});
console.log(tags); // [BookTag, BookTag, BookTag]
console.log(books[0].tags.isInitialized()); // true
console.log(books[0].tags.getItems()); // [BookTag, BookTag, BookTag]

Closes #334