[web-animations] Renamed Timing to AnimationTiming and TimingInput to AnimationTimingInput

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extra : rebase_source : 822f03ff475b39308458cd2fcd601a65739ed2aa
[web-animations] Rename TimedItem to AnimationSource

--HG--
extra : rebase_source : ede81f696575014f82eb4708ef1a970cb7f87c96
[web-animations] Rename 'timed item' to 'animation node'

--HG--
extra : rebase_source : e31612a18d5c67f3cd7974b8caea012a990cc76b