layout: Add initial support for bidirectional text (BiDi) (#33148)

This adds supports for right-to-left text assigning bidi levels to all
line items when necessary. This includes support for the `dir` attribute
as well as corresponding CSS properties like `unicode-bidi`. It only
implements right-to-left rendering for inline layout at the moment and
doesn't include support for `dir=auto`. Because of missing features,
this causes quite a few tests to start failing, as references become
incorrect due to right-to-left rendering being active in some cases,
but not others (before it didn't exist at all).

Analysis of most of the new failures:

```
- /css/css-flexbox/gap-001-rtl.html
  /css/css-flexbox/gap-004-rtl.html
 - Require implementing BiDi in Flexbox, because the start and
   end inline margins are opposite the order of items.

- /css/CSS2/bidi-text/direction-applies-to-*.xht
  /css/CSS2/bidi-text/direction-applies-to-002.xht
  /css/CSS2/bidi-text/direction-applies-to-003.xht
  /css/CSS2/bidi-text/direction-applies-to-004.xht
  - Broken due to a bug in tables, not allocating the
    right amount of width for a column.

- /css/css-lists/inline-list.html
  - This fails because we wrongly insert a soft wrap opportunity between the
    start of an inline box and its first content.

- /css/css-text/bidi/bidi-lines-001.html
  /css/css-text/bidi/bidi-lines-002.html
  /css/CSS2/text/bidi-flag-emoji.html
  - We do not fully support unicode-bidi: plaintext

- /css/css-text/text-align/text-align-end-010.html
  /css/css-text/text-align/text-align-justify-006.html
  /css/css-text/text-align/text-align-start-010.html
  /html/dom/elements/global-attributes/*
  - We do not support dir=auto yet.

- /css/css-text/white-space/tab-bidi-001.html
  - Servo doesn't support tab stops

- /css/CSS2/positioning/abspos-block-level-001.html
  /css/css-text/word-break/word-break-normal-ar-000.html
  - Do not yet support RTL layout in block

- /css/css-text/white-space/pre-wrap-018.html
  - Even in RTL contexts, spaces at the end of the line must hang and
    not be reordered

- /css/css-text/white-space/trailing-space-and-text-alignment-rtl-002.html
  - We are letting spaces hang with white-space: pre, but they shouldn't
    hang.
```

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Rakhi Sharma <atbrakhi@igalia.com>

tests/wpt/meta/css/css-logical/animation-002.html.ini

@@ -3,9 +3,6 @@
   [Logical properties in animations respect the writing-mode]
     expected: FAIL
 
-  [Logical properties in animations respect the direction]
-    expected: FAIL
-
   [Logical properties are able to override physical properties in @keyframes declaration blocks]
     expected: FAIL
 
@@ -26,6 +23,3 @@
 
   [Animations update when the writing-mode is changed through a CSS variable]
     expected: FAIL
-
-  [Animations update when the direction is changed]
-    expected: FAIL

tests/wpt/meta/css/css-logical/animation-004.html.ini

@@ -2,9 +2,6 @@
   [Logical properties in transitions respect the writing-mode]
     expected: FAIL
 
-  [Logical properties in transitions respect the direction]
-    expected: FAIL
-
   [Transitions update when the writing-mode is changed]
     expected: FAIL
 
@@ -20,11 +17,5 @@
   [Transitions update when the writing-mode is changed through a CSS variable]
     expected: FAIL
 
-  [Transitions update when the direction is changed]
-    expected: FAIL
-
-  [Transitions from logical to physical update when the direction is changed]
-    expected: FAIL
-
   [Transitions from physical to logical update when the direction is changed]
     expected: FAIL

tests/wpt/meta/css/css-logical/logical-box-border-shorthands.html.ini

@@ -1,13 +1,4 @@
 [logical-box-border-shorthands.html]
-  [Test that logical border-* properties share computed values with their physical associates, with 'writing-mode: horizontal-tb; direction: rtl; '.]
-    expected: FAIL
-
-  [Test that border-* properties honor order of appearance when both logical and physical associates are declared, with 'writing-mode: horizontal-tb; direction: rtl; '.]
-    expected: FAIL
-
-  [Test that border-* properties honor selector specificty when both logical and physical associates are declared, with 'writing-mode: horizontal-tb; direction: rtl; '.]
-    expected: FAIL
-
   [Test that logical border-* properties share computed values with their physical associates, with 'writing-mode: vertical-rl; direction: rtl; '.]
     expected: FAIL
 

tests/wpt/meta/css/css-logical/logical-values-float-clear-1.html.ini

@@ -1,2 +0,0 @@
-[logical-values-float-clear-1.html]
-  expected: FAIL

tests/wpt/meta/css/css-logical/logical-values-float-clear-2.html.ini

@@ -1,2 +0,0 @@
-[logical-values-float-clear-2.html]
-  expected: FAIL

tests/wpt/meta/css/css-logical/logical-values-float-clear-3.html.ini

@@ -1,2 +0,0 @@
-[logical-values-float-clear-3.html]
-  expected: FAIL

tests/wpt/meta/css/css-logical/logical-values-float-clear-4.html.ini

@@ -1,2 +0,0 @@
-[logical-values-float-clear-4.html]
-  expected: FAIL