Skipping evicted tuples in EE PlanNode Executors

[apavlo]

The goal of this task is to allow the EE's runtime engine ignore tuples that are marked as migrated during query execution. This will allow us to delay when we actually remove a tuple from tables and update indexes. This is very similar to how the anti-caching stuff can identify when it's trying to access an evicted tuple and needs to abort the transaction.

There are only four places in the EE that access tuples directly from PersistantTables:

1. executors/indexscanexecutor
2. executors/nestloopexecutor
3. executors/nestloopindexexecutor
4. executors/seqscanexecutor

If you look at the p_execute() function for each of these classes, you will see a while loop where we iterate over some list of tuples. For IndexScan, you can see where we check TableTuple::isEvicted() for each tuple.

And then this is when I realized that @jdebrabant may not have implemented support for the other parts of the code...