Fixes #1313 - identifiers lost when starting with WITH
Fix flaky shouldNotSnapshotPopulatingIndexes

The test was racing with the population job that was started, because was
initially in a populating state.

The changes introduce a latch, that prevent this population job from completing
before we have taking our snapshot, thus ensuring that the index is indeed
still populating when we take our snapshot.
Ignored flaky test while I debug to allow CI to keep running other stuff.
Merge pull request #1360 from systay/1313

Fixes #1313 - identifiers lost when starting with WITH
Merge pull request #1372 from chrisvest/fix-flaky-shouldNotSnapshotPopulatingIndexes

Fix flaky shouldNotSnapshotPopulatingIndexes
Unused imports.
Ignored another test while I debug it.
Introduce "arguments" into the Expression base class in Cypher

Expression already has "children". The difference between the two
is that children are any expressions hanging off of an expression,
while arguments are arguments into an expression.
Cleanup of aggregation handling.