Remove engine from the constructor arguments `Arel::Table`

It is never used outside of convenience methods which are only used in
tests. In practice, it just made constructing tables more complicated on
the rails side. This is the minimum possible change to remove the
constructor argument, but continue to have the tests passing.

I'm not sure if we have a reason to keep `project` and friends, and the
solution might actually just be to remove the engine from
`SelectManager` and friends. As such I've held off on deleting those
methods.

We need to figure out what to do with `Table#from`. It's old invocation,
which read `table.from(table)` was certainly nonsensical.