Revert "Migrate IDP_GRID_NAME usage to LauncherPrefs"

This reverts commit 6f9a5718.

Reason for revert: A Bug where only device preferences were being used, not the main shared preference file.

Bug: 269569568
Test: Verified this on device.
Change-Id: I8422b2d7073537bd46c3a91033bd2281bbd306b7