Split line layout into two phases (#30089)

In the first phase, we gather LineItems and then when we have enough to
form a line we turn them into Fragments. This will make it possible to
more simply implement `vertical-align` and `text-align: justify` because
we need to measure the different aspects of the candidate line and then
produce a Fragments.

This is a general refactor of the way that inline layout works, so comes
with some progressions. In addition there are some new failures.

New failures:

Some tests are now failing because only the test or reference is getting
proper line height when it wasn't before. These should be fixed in a
followup change that properly calculate line-height in more cases:

 - /_mozilla/css/list_style_position_a.html
 - /css/CSS2/floats/float-no-content-beside-001.html
 - /css/css-content/pseudo-element-inline-box.html
 - /css/css-flexbox/flexbox_flex-none-wrappable-content.html

Some tests are now failing because floats are now placed properly, but
are no longer in their inline box stacking contexts. These will be fixed
by a followup change which properly parents them:

- /css/filter-effects/filtered-inline-applies-to-float.html.ini
- /css/css-color/inline-opacity-float-child.html.ini

One test is failing due to floating point precision errors:

- /css/CSS2/floats-clear/floats-141.xht.ini

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Mukilan Thiyagarajan <mukilan@igalia.com>

components/layout_2020/flow/mod.rs

@@ -372,6 +372,7 @@ impl BlockContainer {
                 positioning_context,
                 containing_block,
                 sequential_layout_state,
+                collapsible_with_parent_start_margin,
             ),
         }
     }