Adds AsRef<[Element]> for Sequence, List, and SExp #3271

Job	Run time
Setup Build Matrix (true, ion-rust, windows, macos, ubuntu, al2-x86, al2-arm, windows, macos, ubu...	1s
Build and Test (windows, default)	4m 11s
Build and Test (windows, all)	4m 5s
Build and Test (windows, experimental-ion-hash)	5m 10s
Build and Test (windows, experimental)	3m 55s
Build and Test (macos, default)	54s
Build and Test (macos, all)	1m 20s
Build and Test (macos, experimental-ion-hash)	1m 44s
Build and Test (macos, experimental)	1m 18s
Build and Test (ubuntu, default)	1m 0s
Build and Test (ubuntu, all)	2m 49s
Build and Test (ubuntu, experimental-ion-hash)	1m 56s
Build and Test (ubuntu, experimental)	1m 42s
Build and Test (al2-x86, default)	1m 5s
Build and Test (al2-x86, all)	1m 27s
Build and Test (al2-x86, experimental-ion-hash)	1m 25s
Build and Test (al2-x86, experimental)	1m 30s
Build and Test (al2-arm, default)	1m 9s
Build and Test (al2-arm, all)	1m 25s
Build and Test (al2-arm, experimental-ion-hash)	1m 16s
Build and Test (al2-arm, experimental)	1m 24s
Build and Test Confirmation	1s
	40m 47s

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