Editor: Specify _fields for parent page selector request

[aduth]

Previously: #12930
Related: #15114

Posts responses can be slow to generate by the REST API. For this reason, it should be considered to optimize the current Parent Page field query to include only the necessary properties to present options in the interface.

Relevant code:

gutenberg/packages/editor/src/components/page-attributes/parent.js

Lines 51 to 63 in 48e06de

	const query = {
	per_page: -1,
	exclude: postId,
	parent_exclude: postId,
	orderby: 'menu_order',
	order: 'asc',
	};
	return {
	parent: getEditedPostAttribute( 'parent' ),
	items: isHierarchical ? getEntityRecords( 'postType', postTypeSlug, query ) : [],
	postType,
	};

[iandunn]

#13618 seems related as a quick glance.

[aduth]

#13618 seems related as a quick glance.

Good call. Let's consolidate there.

[aduth]

Duplicate of #13618