Auto merge of #29799 - stshine:align-self-stretch, r=Loirooriol

layout_2020: Specify the used cross size when replaced item is stretched

According to spec, if the flex item has [align-self: stretch](https://drafts.csswg.org/css-flexbox/#propdef-align-self), redo layout for its contents, treating this used size as its definite cross size so that percentage-sized children can be resolved.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #29788  (GitHub issue number if applicable)

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- [x] There are tests for these changes OR

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components/layout_2020/flow/inline.rs

@@ -573,6 +573,7 @@ fn layout_atomic(
             let size = replaced.contents.used_size_as_if_inline_element(
                 ifc.containing_block,
                 &replaced.style,
+                None,
                 &pbm,
             );
             let fragments = replaced

components/layout_2020/flow/mod.rs

@@ -581,7 +581,7 @@ fn layout_in_flow_replaced_block_level<'a>(
     replaced: &ReplacedContent,
 ) -> BoxFragment {
     let pbm = style.padding_border_margin(containing_block);
-    let size = replaced.used_size_as_if_inline_element(containing_block, style, &pbm);
+    let size = replaced.used_size_as_if_inline_element(containing_block, style, None, &pbm);
 
     let (margin_inline_start, margin_inline_end) =
         solve_inline_margins_for_in_flow_block_level(containing_block, &pbm, size.inline);