Improve arrayFilters auto-rollback behavior

[pp0rtal]

We have added arrayFilters support

• Add arrayFilters support #21
  • feat(21): arrayFilters support with automatic rollback #22

Issue

There is a conflict when we want to $unset a positional property, and $set some static others

    MongoBulkWriteError: Updating the path 'keys.$[element].subKey2.$[element2].elt2' would create a conflict at 'keys'

Hugo gave more details here #22 (comment) with the rollback queries involved.

Workaround for users

• To bypass this issue we omit to backup if we just want to unset a newly added value
  

  mongo-bulk-data-migration/__tests__/MongoBulkDataMigration.rollback.test.ts

  Line 941 in acbe9b7

  projectionBackupFilter: [], // TODO make this unnecessary https://github.com/360Learning/mongo-bulk-data-migration/issues/24

• Or we can in worst case do a custom rollback query and $set back an entire value 8f508a3

Todo

Find a more magic default behavior