Duplicate deletions are swallowed by the consolidation mechanism for Cardinality.LIST in single transaction

If we have addition and multiple deletions for `Cardinality.LIST` then those deletions are swallowed by the consolidation mechanism.

For example, if we have list `A,B,A,C,A,D` and we would like to add `A` to the end and remove two A at front in one transaction so that we would have `B,C,A,D,A` then our deletions will be swallowed and we will have `A,B,A,C,A,D,A`.

More on this can be read here: https://github.com/JanusGraph/janusgraph/pull/1575#discussion_r285275923
Proposed solution which I am not sure yet: https://github.com/JanusGraph/janusgraph/pull/1575#discussion_r285294601
Some related (fixed) issue #1583

Also, I am not sure if it is a bug or not. Maybe it is OK that those deletions are swallowed. I am just creating this issue for now so that we don't lose it.

Start with the Cardinality.LIST consolidation behavior described in this issue and reproduce the A,B,A,C,A,D example within one transaction. Read the discussion on pull request #1575, including the proposed solution, and compare it with related issue #1583. Done means deciding whether duplicate deletions should be preserved and resolving the observed result accordingly.

Written by the indexing model from the issue text.