Auto merge of #14136 - stshine:orthogonal-symmetry, r=SimonSapin

style: Add a "start_end()" method to LogicalMargin

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Add a `LogicalMargin::start_end()` method that receives a `Direction' parameter. This is useful for some layout that is symmetric in inline and block directions, like flexbox.

Part of #14123.

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- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because refactoring

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r? @SimonSapin

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components/layout/construct.rs

@@ -34,7 +34,6 @@ use inline::{FIRST_FRAGMENT_OF_ELEMENT, InlineFlow};
 use inline::{InlineFragmentNodeInfo, LAST_FRAGMENT_OF_ELEMENT};
 use linked_list::prepend_from;
 use list_item::{ListItemFlow, ListStyleTypeContent};
-use model::Direction;
 use multicol::{MulticolColumnFlow, MulticolFlow};
 use parallel;
 use script_layout_interface::{LayoutElementType, LayoutNodeType, is_image_data};
@@ -49,6 +48,7 @@ use style::computed_values::{caption_side, display, empty_cells, float, list_sty
 use style::computed_values::content::ContentItem;
 use style::computed_values::position;
 use style::context::SharedStyleContext;
+use style::logical_geometry::Direction;
 use style::properties::{self, ServoComputedValues};
 use style::selector_impl::{PseudoElement, RestyleDamage};
 use style::selector_matching::Stylist;