[line-clamp] Place the line-clamp ellipsis during line breaking

The current behavior of both `text-overflow: ellipsis` and
`(-webkit-)line-clamp` with respect to positioning the ellipsis is
that after the inline items are positioned, glyphs and other inline
items will be truncated from the visual end of the line until there is
enough space for the ellipsis to fit in the line box, and then the
ellipsis is placed at that position.

For `(-webkit-)line-clamp`, this disagrees with the upcoming
specification, which says that rather than truncating glyphs one by
one, instead all inline content should be truncated until the last
break opportunity where the ellipsis would fit. Furthermore, inline
content should be truncated logically, rather than visually.
And there is an open discussion in
https://github.com/w3c/csswg-drafts/issues/10844 about where the
ellipsis should be positioned in bidi content, which might not be at
the visual end of the line.

This means that the ellipsis should be taken into account at the line
breaking phase. We tried laying out the ellipsis as part of
`LineBreaker` and somehow including it in the `InlineItemResult`s it
produces, but we found it was not always feasible. Instead, we shape
the ellipsis in the `InlineLayoutAlgorithm`, pass its width to
`LineBreaker`, and then in `LogicalLineBuilder` we add a
`LogicalLineItem` for the ellipsis just before bidi reordering.

This also fixes a long-standing bug where lines with the `line-clamp`
ellipsis were not properly aligned or justified (bug 40265829). This
happened because the line content was only trimmed, and the ellipsis
was only shaped, after every `LogicalLineItem` was positioned
according to the alignment and justification. With this patch, since
the trimming and ellipsis shaping happens during line breaking, and
the ellipsis `LogicalLineItem` is created at the same time as other
`LogicalLineItem`s, the ellipsis behaves the same as any other inline
content for alignment and justification.

Some WPT and internal tests break with this change. Some of them are
tests that were written expecting the previous behavior, and probably
need to be updated. But others show that this implementation is
incomplete. Therefore, we are putting this behind the runtime feature
`CSSLineClampLineBreakingEllipsis`.

Bug: 40336192, 40265829
Change-Id: I2d5a645899734b8dea5b0929906b7835b45bd50e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6106171
Reviewed-by: Andreu Botella <abotella@igalia.com>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Andreu Botella <abotella@igalia.com>
Cr-Commit-Position: refs/heads/main@{#1405438}