update - from patch to fully replace

[Idokah]

Delete prepareItemForUpdate and use prepareItemForInsert instead.

For collection with this schema: _id, fieldA, fieldB, update request with this item:
{_id: '..', fieldA: 'whatEver'}, will become in prepareItemsForInsert to :
{_id: '.., fieldA: 'whatEver', fieldB: null}

Until now, this kind of request would only update the fields that the object contains and not override the others.

fixing this issue: https://github.com/wix-private/auto-views/issues/7095

[Idokah]

Will merge after merging #393 to avoid conflicts.