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/fragment_tree/fragment.rs

@@ -299,11 +299,12 @@ impl AnonymousFragment {
 impl TextFragment {
     pub fn print(&self, tree: &mut PrintTree) {
         tree.add_item(format!(
-            "Text num_glyphs={}",
+            "Text num_glyphs={} box={:?}",
             self.glyphs
                 .iter()
                 .map(|glyph_store| glyph_store.len().0)
-                .sum::<isize>()
+                .sum::<isize>(),
+            self.rect,
         ));
     }
 }