[vm] Canonicalize empty Class::interfaces_.
[vm] Canonicalize empty Class::interfaces_.

TEST=ci
Change-Id: I921eb1796b5e142aba8a8f8649a0105ef0e396e4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/243380
Commit-Queue: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@google.com>
Reviewed-by: Alexander Markov <239e774fd29abc1267878f57afe1a8a03e0ca887@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk