Bug 1777320 [wpt PR 34649] - Update CSS toggles parsing/computation code to spec...

Bug 1777320 [wpt PR 34649] - Update CSS toggles parsing/computation code to spec changes., a=testonly

Automatic update from web-platform-tests
Update CSS toggles parsing/computation code to spec changes.

(These properties are behind a runtime flag that is off.)

I believe the complete list of changes is:

 - Toggle states can be described as either custom idents or integers
   rather than only as integers;
   the set of named states (if given) is given inside [] in the
   toggle-root (or toggle) properties; a single named state is given as
   the initial value in toggle-root (or toggle) and after the set verb
   in toggle-trigger.

 - toggle-root (and toggle) take <toggle-states> [at <initial-state>]?
   rather than [<initial-state> /]? <maximum-state>.

 - toggle-root (and toggle) take cycle | cycle-on | sticky, where cycle
   is the default, where there was previously only a (non-default)
   sticky boolean.

 - toggle-trigger has prev/next/set verbs, rather than just taking an
   <integer> (implying set) or nothing (implying 'next 1').

Bug: 1250716
Change-Id: I9f3f2c5d2a681b4e8639ac64d921e2b02ff297a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3735886
Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: David Baron <dbaron@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1019810}

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wpt-commits: 977b25ceff228c792b284df81a4998db6a0345ce
wpt-pr: 34649