23808 add ffi_allocation_patch.dart to libraries.yaml (cla: yes, waiting for tree to go green)

23810 Split platforms for clang in DEPS to prepare for autoroller (cla: yes)

23811 Roll Dart SDK from 0265477b0534 to 970d74c42472 (1 revision) (cla: yes, waiting for tree to go green)

23812 Roll Skia from cdeabcaf5705 to dd069a9188cc (2 revisions) (cla: yes, waiting for tree to go green)

23813 Call Dart plugin registrant if available (cla: yes, waiting for tree to go green)