Bug 1950015 [wpt PR 50896] - Export (mostly anchor positioning related) tests from WebKit, a=testonly

Automatic update from web-platform-tests
Export (mostly anchor positioning related) tests from WebKit

* css/css-anchor-position/try-tactic-basic-anchor.html: add new
  position-try-fallbacks test
* css/css-typed-om/the-stylepropertymap/properties/anchor-scope.html: fix
  case when anchor-scope value is a single identifier. Following the
  reification rules of CSSStyleValue
  (https://drafts.css-houdini.org/css-typed-om-1/#reify-stylevalue),
  a list should be reified as the first iteration of the list.
* web-animations/animation-model/animation-types/property-list.js:
  Add properties previously untested.

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wpt-commits: 6ee4340a397d45ae933cd9e7c12c1686df0713cc
wpt-pr: 50896

UltraBlame original commit: 867f36959b461f58d53e43eb8ed4a2f9376ddc1e

Author: marco-c