[element model] migrate error_verifier (misc. checks)

Change-Id: I04e662a6c95d843975066fc4e64701f5be572d78
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/409880
Commit-Queue: Phil Quitslund <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: pq