Auto merge of #16614 - BorisChiou:stylo/transition/transition_property, r=emilio

stylo: Bug 1357357 - Make the parser of transition-property match the spec.

These are interdependent patches of Bug 1357357. We add one more arm, TransitionProperty::Unsupported, which stores the string of non-animatable, custom, or unrecognized property, so we can parse these kinds of properties and serialize them correctly. This is necessary because we need to start transitions even though some transition-properties are non-animatable, custom, or unrecognized.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix [Bug 1357357](https://bugzilla.mozilla.org/show_bug.cgi?id=1357357).
- [X] There are tests for these changes.

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tests/wpt/metadata-css/css-transitions-1_dev/html/transition-property-002.htm.ini

@@ -6,15 +6,6 @@
   [parse 'all, none']
     expected: FAIL
 
-  [parse 'foobar']
-    expected: FAIL
-
-  [parse 'all, foobar']
-    expected: FAIL
-
-  [parse 'foobar, all']
-    expected: FAIL
-
   [parse 'initial']
     expected: FAIL