[vm, compiler] Fold UnboxInt32(Constant(Mint)) and UnboxDouble(Constant(Mint)) to UnboxedConstant.
[vm, compiler] Fold UnboxInt32(Constant(Mint)) and UnboxDouble(Constant(Mint)) to UnboxedConstant.

ConstantPropagator_Regress35371 notices the former fails to happen with compressed Smis.

TEST=ci
Change-Id: I4d1e974deec8515469dac4db79dfb0521d3a6e7f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/181960
Reviewed-by: Alexander Markov <239e774fd29abc1267878f57afe1a8a03e0ca887@google.com>
Commit-Queue: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@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