layout: Linebreak the entire InlineFormattingContext at once (#32483)

Instead of linebreaking inside each single-font text segment, linebreak
the entire inline formatting context at once. This has several benefits:

1. It allows us to use `icu_segmenter` (already in use from style),
   which is written against a newer version of the Unicode spec --
   preventing breaking emoji clusters.
2. Opens up the possibility of changing the way that linebreaking and
   shaping work -- eventually allowing shaping across inline box
   boundaries and line breaking *after* shaping.

Co-authored-by: Rakhi Sharma <atbrakhi@igalia.com>

tests/wpt/meta/css/css-text/word-break/word-break-manual-001.html.ini

@@ -0,0 +1,2 @@
+[word-break-manual-001.html]
+  expected: FAIL

tests/wpt/meta/css/css-text/word-break/word-break-normal-002.html.ini

@@ -1,2 +0,0 @@
-[word-break-normal-002.html]
-  expected: FAIL

tests/wpt/meta/css/css-text/word-break/word-break-normal-003.html.ini

@@ -1,2 +0,0 @@
-[word-break-normal-003.html]
-  expected: FAIL

tests/wpt/meta/css/css-text/word-break/word-break-normal-th-000.html.ini

@@ -1,2 +0,0 @@
-[word-break-normal-th-000.html]
-  expected: FAIL

tests/wpt/meta/css/css-text/word-break/word-break-normal-th-001.html.ini

@@ -1,2 +0,0 @@
-[word-break-normal-th-001.html]
-  expected: FAIL