Auto merge of #29887 - Loirooriol:float-inline-size-complete, r=mrobinson

Handle floats in BlockContainer::inline_content_sizes

Typically, block-level contents are stacked vertically, so this was just taking the maximum size among all contents. However, floats can be stacked horizontally, so we need to sum their sizes.

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---
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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 #29874

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

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tests/wpt/metadata-layout-2020/css/css-flexbox/flex-basis-intrinsics-001.html.ini

@@ -1,4 +1,7 @@
 [flex-basis-intrinsics-001.html]
+  [.flex-item 1]
+    expected: FAIL
+
   [.flex-item 2]
     expected: FAIL
 
@@ -20,11 +23,5 @@
   [.flex-item 6]
     expected: FAIL
 
-  [.flex-item 7]
-    expected: FAIL
-
-  [.flex-item 9]
-    expected: FAIL
-
   [.flex-item 11]
     expected: FAIL