Support transaction rollback of ent commits

[chipsenkbeil]

Provide some API to facilitate transactions where all commits succeed or none do, rather than a mixture.

First thought is that we'd provide some wrapper like

db.transaction(|inner_db| {
  // Use inner_db here, which is a wrapper around a database that records the id of every ent committed along with the previous state of the ent to reset
});

In the case of using a global database, something similar can be applied

global::transaction(|db| {
  // db is just a facade around the usage of global::with_db which has also set the database to the wrapper globally and will swap back to non-wrapped version after?
});