Resolve keyProperty access conflicts when using Mapped Fields in Turbo Mode (autoInitRecords: false).

The Problem:

1. Turbo Mode: Store holds raw objects. keyProperty points to the raw data key (e.g. 'l'). rawItem['l'] works.
2. Lazy Instantiation: When accessed, raw objects become Records. RecordFactory creates getters for canonical field names (e.g. login), but NOT for mapped source keys. record['l'] is undefined.
3. Selection Model: Uses record[store.getKeyProperty()]. If keyProperty is 'l', this fails on instantiated records.

The Fix:

1. Neo.data.Store#getKey(item): Implement a helper method to resolve the key regardless of item type.
   • Try item[keyProp].
   • If undefined & item is Record, try item.get(keyProp).
2. Refactor Selection Models: Update RowModel (and others) to use store.getKey(record) instead of direct access.

Goal: Transparently support mapped key properties in mixed Raw/Record environments.