get_block_wrapper_attributes: Ensures that user-provided attributes override the attributes generated by block supports

[t-hamano]

Trac ticket: https://core.trac.wordpress.org/ticket/64603

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[westonruter]

Just realizing the logic here can be simplified a bit by having a single array that contains the attributes to merge or override:

	// This is hardcoded on purpose.
	// We only support a fixed list of attributes.
	$handled_attributes = array(
		'style'      => true,
		'class'      => true,
		'id'         => false,
		'aria-label' => false,
	);
	$attributes         = array();
	foreach ( $handled_attributes as $attribute_name => $is_merged ) {
		if ( empty( $new_attributes[ $attribute_name ] ) && empty( $extra_attributes[ $attribute_name ] ) ) {
			continue;
		}

		if ( empty( $new_attributes[ $attribute_name ] ) ) {
			$attributes[ $attribute_name ] = $extra_attributes[ $attribute_name ];
			continue;
		}

		if ( empty( $extra_attributes[ $attribute_name ] ) ) {
			$attributes[ $attribute_name ] = $new_attributes[ $attribute_name ];
			continue;
		}

		if ( $is_merged ) {
			$attributes[ $attribute_name ] = $extra_attributes[ $attribute_name ] . ' ' . $new_attributes[ $attribute_name ];
		} else {
			$attributes[ $attribute_name ] = $extra_attributes[ $attribute_name ];
		}
	}

	foreach ( $extra_attributes as $attribute_name => $value ) {
		if ( ! isset( $handled_attributes[ $attribute_name ] ) ) {
			$attributes[ $attribute_name ] = $value;
		}
	}

[westonruter]

Shouldn't id and aria-label be removed from this list?

[westonruter]

Naturally this is irrelevant if #10877 (comment) is adopted.

[westonruter]

In the case of merging style, should special handling be added to ensure that $extra_attributes[ $attribute_name ] ends in a semicolon? The current empty space is only really appropriate for class.