Use DeviceProfile numFolderRows and numFolderColumns

Invariant hold values that are not related to current DP in use. This is a change needed for IDP to hold more values in the future akin to iconSize.

Bug: 309800141
Change-Id: Iefb388a5f6590d7da3452d2c388c02bd5e9d32bb
Flag: N/A
Test: NexusLauncherTests