fix/164: Show pagination when Sort by Order is clicked

[Sidsector9]

Closes #164

Description of the Change

In this PR, we additionally send posts_per_page as -1 when "Sort By Order" is clicked to enable pagination.

How to test the Change

Changelog Entry

Fixed - Hidden pagination in admin screen when Sort by Order is clicked

Credits

Props @tlovett1 @dkotter @Sidsector9

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[dkotter]

While this does appear to fix the pagination issue, what I'm seeing is it will no longer show the page heirarchy. For instance, if I have a parent page with multiple child pages, on the main list view, those are shown as nested beneath the parent. If I click on Sort by order prior to this fix, that nesting is still shown, though pagination doesn't show. With the changes in this PR, if I click on Sort by order, pagination now shows but the nesting heirarchy is lost

[Sidsector9]

@dkotter that's a good catch. I took an alternative approach and tested it with child, as well as child of child elements. Can you take a look?

[peterwilsoncc]

This will affect all queries on the page, not just the main query for the list table.

It's probably going to need:

			if ( ! $query->is_main_query() ) {
				return;
			}

[peterwilsoncc]

No need to sanitize or unslash when comparing to a string that requires neither.

Suggested change

	$is_simple_page_ordering = isset( $_GET['id'] ) ? 'simple-page-ordering' === sanitize_text_field( wp_unslash( $_GET['id'] ) ) : false;
	// phpcs:ignore WordPress.Security.NonceVerification.Recommended
	$is_simple_page_ordering = isset( $_GET['id'] ) ? 'simple-page-ordering' === $_GET['id'] : false;

[peterwilsoncc]

LGTM and passes manual testing.

The E2E tests failed on the first run but it appears to have been a glitch as they passed on the second run.